Can't get SSL working on nginx / Raspberry PI

Hello and kind regards from Switzerland.

First of all I am not a native speaker so please excuse any humble or strange expression. Thanks in advance!

I am not new to setting up mostly Apache based servers hosted on my own computers (I once had the very first CERN html sites hosted on a Macintosh Plus with 4 MB of RAM and a NextCube for documentation purposes) but I am new to nginx. I am hosting my WordPress installation on a Raspberry Pi 5 with 16 GB of RAM. I followed the installation guides of PHP, phpMyAdmin, MySQL and nginx on PiMyLifeUp. And now I want to use SSL on my nginx server.
My domain uses No-IP. My Plex server and my SFTP server are running fine, no troubles here.

I installed certbot and linked it to Let's encrypt, I double-checked that certificates are installed. Renewing with

sudo certbot renew

is not possible as they expire somewhere within the next 80 days so I guess the certificates a) are installed and b) are installed in the right place. So far so good.

Before installing certbot for nginx I could reach my Wordpress page locally and from the internet without any troubles as https was not implemented. After installing certbot, the certificates and else on my Raspberry Pi (not using any docker installations) I still can reach my WordPress installation by using the local IP adress (made static by my router) and using "https://". Whenever reaching out to my WordPress installation from somewhere else outside my local network something odd is happening. Typing the domain name ("registered" at No-IP) like "https://example.ddns.net" followed by the WordPress login " .../wp-admin/ " all of my browsers change to "https://IP-adress of Raspberry Pi/wp-admin/". I am not able to log into my WordPress installation outside my local network as the server is not found.

I've been fiddling around with nginx configuration files many hours by now still not understanding where the problem is. Whenever using

nginx -t

or

nginx -T

or variants of this using sudo terminal throws me this:

2025/05/19 16:16:02 [warn] 20899#20899: the "user" directive makes sense only if the master process runs with super-user privileges, ignored in /etc/nginx/nginx.conf:1
2025/05/19 16:16:02 [emerg] 20899#20899: cannot load certificate "/etc/letsencrypt/live/mychosen.ddns.net/fullchain.pem": BIO_new_file() failed (SSL: error:8000000D:system library::Permission denied:calling fopen(/etc/letsencrypt/live/mychosenname.ddns.net/fullchain.pem, r) error:10080002:BIO routines::system lib)

I changed the rights on fullchain.pem to 644 and 777 in between but the error message stays the same. I am pretty sure that I made the chown process as sudo, so I do not understand why nginx (or the www user) still isn't able to pick up the certificates. Furthermore I am not able to get a solution for another strange behaviour. Whenever using

systemctl status nginx.service

terminal throws me this:

Mai 19 14:41:38 raspberrypi systemd[1]: Starting nginx.service - A high performance web server and a reverse proxy server...
Mai 19 14:41:38 raspberrypi nginx[17106]: 2025/05/19 14:41:38 [warn] 17106#17106: conflicting server name "chosenname.ddns.net" on 0.0.0.0:80, ignored
Mai 19 14:41:38 raspberrypi nginx[17106]: 2025/05/19 14:41:38 [warn] 17106#17106: conflicting server name "chosenname.ddns.net" on [::]:80, ignored
Mai 19 14:41:38 raspberrypi nginx[17106]: 2025/05/19 14:41:38 [warn] 17106#17106: conflicting server name "chosenname.ddns.net" on 0.0.0.0:443, ignored
Mai 19 14:41:38 raspberrypi nginx[17107]: 2025/05/19 14:41:38 [warn] 17107#17107: conflicting server name "chosenname.ddns.net" on 0.0.0.0:80, ignored
Mai 19 14:41:38 raspberrypi nginx[17107]: 2025/05/19 14:41:38 [warn] 17107#17107: conflicting server name "chosenname.ddns.net" on [::]:80, ignored
Mai 19 14:41:38 raspberrypi nginx[17107]: 2025/05/19 14:41:38 [warn] 17107#17107: conflicting server name "chosenname.ddns.net" on 0.0.0.0:443, ignored
Mai 19 14:41:38 raspberrypi systemd[1]: Started nginx.service - A high performance web server and a reverse proxy server.

As far as I understand this message by now my nginx seems to have at least two server block definitions unsing the same domain name. Am I right? It took my at least three hours to find out that the standard nginx configuration file has dependencies from a "default" file.... I am pretty stuck by now and any help is very appreciated! Thanks for any possible reply!

Jens

Hello @Jens_Liedtke,

How was Certbot installed?

Please share the links to those gudes.

Please show the output of each of the following commands

  • sudo certbot --version
  • sudo certbot certificates
  • sudo nginx -T that is a capital T
1 Like

(post deleted by author)

Hello Bruce.

Thanks for taking a look into my request! Before getting into detail I would like to note that I re-installed Nginx (phpMyAdmin, MariaDB, PHP and several other things) several times, always ending up with more or less the same behaviour. Now the details... I followed the guide at

as it is covering not only Apache but Nginx, too. Before I had Pi-Hole 6 running, also several times re-installed (but now uninstalled). I did not use Pi-Hole as DNS or DHCP server. Pi-Hole some times interfered with my port forwarding as it was not using alternative ports the way it was supposed to. After deleting Pi-Hole and re-installing the complete NGinx-related server stuff the port problems have gone. Additional not: I was always able to ssh into my Raspberry Pi within the local network and from the outside. Now for the certbot stuff. Installed version is

certbot 2.1.0

As far as I know the most actual version. Now the certificates (please note that I am not providing the real name chosen with "No-IP" and in cases not the real IP of the Raspberry Pi within my network):

Found the following certs:
  Certificate Name: mychosenname.ddns.net
    Serial Number: 652df46e172c3bb669142bcc7d246b4a51c
    Key Type: ECDSA
    Domains: mychosenname.ddns.net
    Expiry Date: 2025-08-17 09:13:56+00:00 (VALID: 89 days)
    Certificate Path: /etc/letsencrypt/live/mychosenname.ddns.net/fullchain.pem
    Private Key Path: /etc/letsencrypt/live/mychosenname.ddns.net/privkey.pem

As You can see the certificates can not be renewed. I've been looking around the directories. At the given location of fullchain.pem and privkey.pem are just alias files stored, the real files are stored within /etc/letsencrypt/archive/ . I can not access that directory as normal user (but by sudo). In addition the file prefixes over there contain an additional "1* within their filenames at the end. Now for the big one (sudo nginx -T):

5/05/20 07:23:30 [warn] 63532#63532: conflicting server name "mychosenname.ddns.net" on 0.0.0.0:80, ignored
2025/05/20 07:23:30 [warn] 63532#63532: conflicting server name "mychosenname.ddns.net" on [::]:80, ignored
2025/05/20 07:23:30 [warn] 63532#63532: conflicting server name "mychosenname.ddns.net" on 0.0.0.0:443, ignored
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
# configuration file /etc/nginx/nginx.conf:
user www-data;
worker_processes auto;
pid /run/nginx.pid;
error_log /var/log/nginx/error.log;
include /etc/nginx/modules-enabled/*.conf;

events {
	worker_connections 768;
	# multi_accept on;
}

http {

	##
	# Basic Settings
	##

	sendfile on;
	tcp_nopush on;
	types_hash_max_size 2048;
	# server_tokens off;

	# server_names_hash_bucket_size 64;
	# server_name_in_redirect off;

	include /etc/nginx/mime.types;
	default_type application/octet-stream;

	##
	# SSL Settings
	##

	ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3; # Dropping SSLv3, ref: POODLE
	ssl_prefer_server_ciphers on;

	##
	# Logging Settings
	##

	access_log /var/log/nginx/access.log;

	##
	# Gzip Settings
	##

	gzip on;

	# gzip_vary on;
	# gzip_proxied any;
	# gzip_comp_level 6;
	# gzip_buffers 16 8k;
	# gzip_http_version 1.1;
	# gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;

	##
	# Virtual Host Configs
	##

	include /etc/nginx/conf.d/*.conf;
	include /etc/nginx/sites-enabled/*;
}


#mail {
#	# See sample authentication script at:
#	# http://wiki.nginx.org/ImapAuthenticateWithApachePhpScript
#
#	# auth_http localhost/auth.php;
#	# pop3_capabilities "TOP" "USER";
#	# imap_capabilities "IMAP4rev1" "UIDPLUS";
#
#	server {
#		listen     localhost:110;
#		protocol   pop3;
#		proxy      on;
#	}
#
#	server {
#		listen     localhost:143;
#		protocol   imap;
#		proxy      on;
#	}
#}


# configuration file /etc/nginx/mime.types:

types {
    text/html                             html htm shtml;
    text/css                              css;
    text/xml                              xml;
    image/gif                             gif;
    image/jpeg                            jpeg jpg;
    application/javascript                js;
    application/atom+xml                  atom;
    application/rss+xml                   rss;

    text/mathml                           mml;
    text/plain                            txt;
    text/vnd.sun.j2me.app-descriptor      jad;
    text/vnd.wap.wml                      wml;
    text/x-component                      htc;

    image/avif                            avif;
    image/png                             png;
    image/svg+xml                         svg svgz;
    image/tiff                            tif tiff;
    image/vnd.wap.wbmp                    wbmp;
    image/webp                            webp;
    image/x-icon                          ico;
    image/x-jng                           jng;
    image/x-ms-bmp                        bmp;

    font/woff                             woff;
    font/woff2                            woff2;

    application/java-archive              jar war ear;
    application/json                      json;
    application/mac-binhex40              hqx;
    application/msword                    doc;
    application/pdf                       pdf;
    application/postscript                ps eps ai;
    application/rtf                       rtf;
    application/vnd.apple.mpegurl         m3u8;
    application/vnd.google-earth.kml+xml  kml;
    application/vnd.google-earth.kmz      kmz;
    application/vnd.ms-excel              xls;
    application/vnd.ms-fontobject         eot;
    application/vnd.ms-powerpoint         ppt;
    application/vnd.oasis.opendocument.graphics        odg;
    application/vnd.oasis.opendocument.presentation    odp;
    application/vnd.oasis.opendocument.spreadsheet     ods;
    application/vnd.oasis.opendocument.text            odt;
    application/vnd.openxmlformats-officedocument.presentationml.presentation    pptx;
    application/vnd.openxmlformats-officedocument.spreadsheetml.sheet    xlsx;
    application/vnd.openxmlformats-officedocument.wordprocessingml.document    docx;
    application/vnd.wap.wmlc              wmlc;
    application/wasm                      wasm;
    application/x-7z-compressed           7z;
    application/x-cocoa                   cco;
    application/x-java-archive-diff       jardiff;
    application/x-java-jnlp-file          jnlp;
    application/x-makeself                run;
    application/x-perl                    pl pm;
    application/x-pilot                   prc pdb;
    application/x-rar-compressed          rar;
    application/x-redhat-package-manager  rpm;
    application/x-sea                     sea;
    application/x-shockwave-flash         swf;
    application/x-stuffit                 sit;
    application/x-tcl                     tcl tk;
    application/x-x509-ca-cert            der pem crt;
    application/x-xpinstall               xpi;
    application/xhtml+xml                 xhtml;
    application/xspf+xml                  xspf;
    application/zip                       zip;

    application/octet-stream              bin exe dll;
    application/octet-stream              deb;
    application/octet-stream              dmg;
    application/octet-stream              iso img;
    application/octet-stream              msi msp msm;

    audio/midi                            mid midi kar;
    audio/mpeg                            mp3;
    audio/ogg                             ogg;
    audio/x-m4a                           m4a;
    audio/x-realaudio                     ra;

    video/3gpp                            3gpp 3gp;
    video/mp2t                            ts;
    video/mp4                             mp4;
    video/mpeg                            mpeg mpg;
    video/quicktime                       mov;
    video/webm                            webm;
    video/x-flv                           flv;
    video/x-m4v                           m4v;
    video/x-mng                           mng;
    video/x-ms-asf                        asx asf;
    video/x-ms-wmv                        wmv;
    video/x-msvideo                       avi;
}

# configuration file /etc/nginx/sites-enabled/default:
##
# You should look at the following URL's in order to grasp a solid understanding
# of Nginx configuration files in order to fully unleash the power of Nginx.
# https://www.nginx.com/resources/wiki/start/
# https://www.nginx.com/resources/wiki/start/topics/tutorials/config_pitfalls/
# https://wiki.debian.org/Nginx/DirectoryStructure
#
# In most cases, administrators will remove this file from sites-enabled/ and
# leave it as reference inside of sites-available where it will continue to be
# updated by the nginx packaging team.
#
# This file will automatically load configuration files provided by other
# applications, such as Drupal or Wordpress. These applications will be made
# available underneath a path with that package name, such as /drupal8.
#
# Please see /usr/share/doc/nginx-doc/examples/ for more detailed examples.
##

# Default server configuration
#
server {
	listen 80 default_server;
	listen [::]:80 default_server;

	listen 443 ssl;

	# SSL configuration
	#
	# listen 443 ssl default_server;
	# listen [::]:443 ssl default_server;
	#
	# Note: You should disable gzip for SSL traffic.
	# See: https://bugs.debian.org/773332
	#
	# Read up on ssl_ciphers to ensure a secure configuration.
	# See: https://bugs.debian.org/765782
	#
	# Self signed certs generated by the ssl-cert package
	# Don't use them in a production server!
	#
	# include snippets/snakeoil.conf;

	root /var/www/html;

	# Add index.php to the list if you are using PHP
	index index.php index.html index.htm index.nginx-debian.html;

	server_name mychosenname.ddns.net;

	ssl_certificate /etc/letsencrypt/live/mychosenname.ddns.net/fullchain.pem;
	ssl_certificate_key /etc/letsencrypt/live/mychosenname.ddns.net/privkey.pem;

	location / {
		# First attempt to serve request as file, then
		# as directory, then fall back to displaying a 404.
		try_files $uri $uri/ =404;
	}

	# pass PHP scripts to FastCGI server
	#
	location ~ \.php$ {
               include snippets/fastcgi-php.conf;
               fastcgi_pass unix:/var/run/php/php8.2-fpm.sock;
        }

	# deny access to .htaccess files, if Apache's document root
	# concurs with nginx's one
	#
	#location ~ /\.ht {
	#	deny all;
	#}
}


# Virtual Host configuration for example.com
#
# You can move that to a different file under sites-available/ and symlink that
# to sites-enabled/ to enable it.
#
#server {
#	listen 80;
#	listen [::]:80;
#
#	server_name example.com;
#
#	root /var/www/example.com;
#	index index.html;
#
#	location / {
#		try_files $uri $uri/ =404;
#	}
#}

server {

	# SSL configuration
	#
	# listen 443 ssl default_server;
	# listen [::]:443 ssl default_server;
	#
	# Note: You should disable gzip for SSL traffic.
	# See: https://bugs.debian.org/773332
	#
	# Read up on ssl_ciphers to ensure a secure configuration.
	# See: https://bugs.debian.org/765782
	#
	# Self signed certs generated by the ssl-cert package
	# Don't use them in a production server!
	#
	# include snippets/snakeoil.conf;

	root /var/www/html;

	# Add index.php to the list if you are using PHP
	index index.php index.html index.htm index.nginx-debian.html;
    server_name mychosenname.ddns.net; # managed by Certbot


	location / {
		# First attempt to serve request as file, then
		# as directory, then fall back to displaying a 404.
		try_files $uri $uri/ =404;
	}

	# pass PHP scripts to FastCGI server
	#
	location ~ \.php$ {
               include snippets/fastcgi-php.conf;
               fastcgi_pass unix:/var/run/php/php8.2-fpm.sock;
        }

	# deny access to .htaccess files, if Apache's document root
	# concurs with nginx's one
	#
	#location ~ /\.ht {
	#	deny all;
	#}


    listen [::]:443 ssl ipv6only=on; # managed by Certbot
    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/mychosenname.ddns.net/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/mychosenname.ddns.net/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

}
server {
    if ($host = mychosenname.ddns.net) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


	listen 80 ;
	listen [::]:80 ;
    server_name mychosenname.ddns.net;
    return 404; # managed by Certbot


}

# configuration file /etc/nginx/snippets/fastcgi-php.conf:
# regex to split $uri to $fastcgi_script_name and $fastcgi_path
fastcgi_split_path_info ^(.+?\.php)(/.*)$;

# Check that the PHP script exists before passing it
try_files $fastcgi_script_name =404;

# Bypass the fact that try_files resets $fastcgi_path_info
# see: http://trac.nginx.org/nginx/ticket/321
set $path_info $fastcgi_path_info;
fastcgi_param PATH_INFO $path_info;

fastcgi_index index.php;
include fastcgi.conf;

# configuration file /etc/nginx/fastcgi.conf:

fastcgi_param  SCRIPT_FILENAME    $document_root$fastcgi_script_name;
fastcgi_param  QUERY_STRING       $query_string;
fastcgi_param  REQUEST_METHOD     $request_method;
fastcgi_param  CONTENT_TYPE       $content_type;
fastcgi_param  CONTENT_LENGTH     $content_length;

fastcgi_param  SCRIPT_NAME        $fastcgi_script_name;
fastcgi_param  REQUEST_URI        $request_uri;
fastcgi_param  DOCUMENT_URI       $document_uri;
fastcgi_param  DOCUMENT_ROOT      $document_root;
fastcgi_param  SERVER_PROTOCOL    $server_protocol;
fastcgi_param  REQUEST_SCHEME     $scheme;
fastcgi_param  HTTPS              $https if_not_empty;

fastcgi_param  GATEWAY_INTERFACE  CGI/1.1;
fastcgi_param  SERVER_SOFTWARE    nginx/$nginx_version;

fastcgi_param  REMOTE_ADDR        $remote_addr;
fastcgi_param  REMOTE_PORT        $remote_port;
fastcgi_param  REMOTE_USER        $remote_user;
fastcgi_param  SERVER_ADDR        $server_addr;
fastcgi_param  SERVER_PORT        $server_port;
fastcgi_param  SERVER_NAME        $server_name;

# PHP only, required if PHP was built with --enable-force-cgi-redirect
fastcgi_param  REDIRECT_STATUS    200;

# configuration file /etc/letsencrypt/options-ssl-nginx.conf:
# This file contains important security parameters. If you modify this file
# manually, Certbot will be unable to automatically provide future security
# updates. Instead, Certbot will print and log an error message with a path to
# the up-to-date file that you will need to refer to when manually updating
# this file. Contents are based on https://ssl-config.mozilla.org

ssl_session_cache shared:le_nginx_SSL:10m;
ssl_session_timeout 1440m;
ssl_session_tickets off;

ssl_protocols TLSv1.2 TLSv1.3;
ssl_prefer_server_ciphers off;

ssl_ciphers "ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384";

In addition I would like to provide the Nginx configuration. Please have in mind that it took me some hours to find out that any SSL related modifications can NOT be placed into "nginx.conf" located at /etc/nginx . Modifications have to be made into the file "default" (no suffix...) located at /etc/nginx/sites-available/ . The only "error" I can think off regarding that configuration file is the fact "server" is appearing two times but I am not sure about that one:


# You should look at the following URL's in order to grasp a solid understanding
# of Nginx configuration files in order to fully unleash the power of Nginx.
# https://www.nginx.com/resources/wiki/start/
# https://www.nginx.com/resources/wiki/start/topics/tutorials/config_pitfalls/
# https://wiki.debian.org/Nginx/DirectoryStructure
#
# In most cases, administrators will remove this file from sites-enabled/ and
# leave it as reference inside of sites-available where it will continue to be
# updated by the nginx packaging team.
#
# This file will automatically load configuration files provided by other
# applications, such as Drupal or Wordpress. These applications will be made
# available underneath a path with that package name, such as /drupal8.
#
# Please see /usr/share/doc/nginx-doc/examples/ for more detailed examples.
##

# Default server configuration
#
server {
	listen 80 default_server;
	listen [::]:80 default_server;

	listen 443 ssl;

	# SSL configuration
	#
	# listen 443 ssl default_server;
	# listen [::]:443 ssl default_server;
	#
	# Note: You should disable gzip for SSL traffic.
	# See: https://bugs.debian.org/773332
	#
	# Read up on ssl_ciphers to ensure a secure configuration.
	# See: https://bugs.debian.org/765782
	#
	# Self signed certs generated by the ssl-cert package
	# Don't use them in a production server!
	#
	# include snippets/snakeoil.conf;

	root /var/www/html;

	# Add index.php to the list if you are using PHP
	index index.php index.html index.htm index.nginx-debian.html;

	server_name mychosenname.ddns.net;

	ssl_certificate /etc/letsencrypt/live/mychosenname.ddns.net/fullchain.pem;
	ssl_certificate_key /etc/letsencrypt/live/mychosenname.ddns.net/privkey.pem;

	location / {
		# First attempt to serve request as file, then
		# as directory, then fall back to displaying a 404.
		try_files $uri $uri/ =404;
	}

	# pass PHP scripts to FastCGI server
	#
	location ~ \.php$ {
               include snippets/fastcgi-php.conf;
               fastcgi_pass unix:/var/run/php/php8.2-fpm.sock;
        }

	# deny access to .htaccess files, if Apache's document root
	# concurs with nginx's one
	#
	#location ~ /\.ht {
	#	deny all;
	#}
}


# Virtual Host configuration for example.com
#
# You can move that to a different file under sites-available/ and symlink that
# to sites-enabled/ to enable it.
#
#server {
#	listen 80;
#	listen [::]:80;
#
#	server_name example.com;
#
#	root /var/www/example.com;
#	index index.html;
#
#	location / {
#		try_files $uri $uri/ =404;
#	}
#}

server {

	# SSL configuration
	#
	# listen 443 ssl default_server;
	# listen [::]:443 ssl default_server;
	#
	# Note: You should disable gzip for SSL traffic.
	# See: https://bugs.debian.org/773332
	#
	# Read up on ssl_ciphers to ensure a secure configuration.
	# See: https://bugs.debian.org/765782
	#
	# Self signed certs generated by the ssl-cert package
	# Don't use them in a production server!
	#
	# include snippets/snakeoil.conf;

	root /var/www/html;

	# Add index.php to the list if you are using PHP
	index index.php index.html index.htm index.nginx-debian.html;
    server_name mychosenname.ddns.net; # managed by Certbot


	location / {
		# First attempt to serve request as file, then
		# as directory, then fall back to displaying a 404.
		try_files $uri $uri/ =404;
	}

	# pass PHP scripts to FastCGI server
	#
	location ~ \.php$ {
               include snippets/fastcgi-php.conf;
               fastcgi_pass unix:/var/run/php/php8.2-fpm.sock;
        }

	# deny access to .htaccess files, if Apache's document root
	# concurs with nginx's one
	#
	#location ~ /\.ht {
	#	deny all;
	#}


    listen [::]:443 ssl ipv6only=on; # managed by Certbot
    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/mychosenname.ddns.net/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/mychosenname.ddns.net/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

}
server {
    if ($host = mychosenname.ddns.net) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


	listen 80 ;
	listen [::]:80 ;
    server_name mychosenname.ddns.net;
    return 404; # managed by Certbot


}

# configuration file /etc/nginx/snippets/fastcgi-php.conf:
# regex to split $uri to $fastcgi_script_name and $fastcgi_path
fastcgi_split_path_info ^(.+?\.php)(/.*)$;

# Check that the PHP script exists before passing it
try_files $fastcgi_script_name =404;

# Bypass the fact that try_files resets $fastcgi_path_info
# see: http://trac.nginx.org/nginx/ticket/321
set $path_info $fastcgi_path_info;
fastcgi_param PATH_INFO $path_info;

fastcgi_index index.php;
include fastcgi.conf;

# configuration file /etc/nginx/fastcgi.conf:

fastcgi_param  SCRIPT_FILENAME    $document_root$fastcgi_script_name;
fastcgi_param  QUERY_STRING       $query_string;
fastcgi_param  REQUEST_METHOD     $request_method;
fastcgi_param  CONTENT_TYPE       $content_type;
fastcgi_param  CONTENT_LENGTH     $content_length;

fastcgi_param  SCRIPT_NAME        $fastcgi_script_name;
fastcgi_param  REQUEST_URI        $request_uri;
fastcgi_param  DOCUMENT_URI       $document_uri;
fastcgi_param  DOCUMENT_ROOT      $document_root;
fastcgi_param  SERVER_PROTOCOL    $server_protocol;
fastcgi_param  REQUEST_SCHEME     $scheme;
fastcgi_param  HTTPS              $https if_not_empty;

fastcgi_param  GATEWAY_INTERFACE  CGI/1.1;
fastcgi_param  SERVER_SOFTWARE    nginx/$nginx_version;

fastcgi_param  REMOTE_ADDR        $remote_addr;
fastcgi_param  REMOTE_PORT        $remote_port;
fastcgi_param  REMOTE_USER        $remote_user;
fastcgi_param  SERVER_ADDR        $server_addr;
fastcgi_param  SERVER_PORT        $server_port;
fastcgi_param  SERVER_NAME        $server_name;

# PHP only, required if PHP was built with --enable-force-cgi-redirect
fastcgi_param  REDIRECT_STATUS    200;

# configuration file /etc/letsencrypt/options-ssl-nginx.conf:
# This file contains important security parameters. If you modify this file
# manually, Certbot will be unable to automatically provide future security
# updates. Instead, Certbot will print and log an error message with a path to
# the up-to-date file that you will need to refer to when manually updating
# this file. Contents are based on https://ssl-config.mozilla.org

ssl_session_cache shared:le_nginx_SSL:10m;
ssl_session_timeout 1440m;
ssl_session_tickets off;

ssl_protocols TLSv1.2 TLSv1.3;
ssl_prefer_server_ciphers off;

ssl_ciphers "ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384";

pi@raspberrypi:~ $ sudo nano /etc/nginx/sites-available/default

  GNU nano 7.2                                                              /etc/nginx/sites-available/default                                                                        
##
# You should look at the following URL's in order to grasp a solid understanding
# of Nginx configuration files in order to fully unleash the power of Nginx.
# https://www.nginx.com/resources/wiki/start/
# https://www.nginx.com/resources/wiki/start/topics/tutorials/config_pitfalls/
# https://wiki.debian.org/Nginx/DirectoryStructure
#
# In most cases, administrators will remove this file from sites-enabled/ and
# leave it as reference inside of sites-available where it will continue to be
# updated by the nginx packaging team.
#
# This file will automatically load configuration files provided by other
# applications, such as Drupal or Wordpress. These applications will be made
# available underneath a path with that package name, such as /drupal8.
#
# Please see /usr/share/doc/nginx-doc/examples/ for more detailed examples.
##

# Default server configuration
#
server {
        listen 80 default_server;
        listen [::]:80 default_server;

        listen 443 ssl;

        # SSL configuration
        #
        # listen 443 ssl default_server;
        # listen [::]:443 ssl default_server;
        #
        # Note: You should disable gzip for SSL traffic.
        # See: https://bugs.debian.org/773332
        #
        # Read up on ssl_ciphers to ensure a secure configuration.
        # See: https://bugs.debian.org/765782
        #
        # Self signed certs generated by the ssl-cert package
        # Don't use them in a production server!
        #
        # include snippets/snakeoil.conf;

        root /var/www/html;

        # Add index.php to the list if you are using PHP
        index index.php index.html index.htm index.nginx-debian.html;

        server_name mychosenname.ddns.net;

        ssl_certificate /etc/letsencrypt/live/mychosenname.ddns.net/fullchain.pem;
        ssl_certificate_key /etc/letsencrypt/live/mychosenname.ddns.net/privkey.pem;

        location / {
                # First attempt to serve request as file, then
                # as directory, then fall back to displaying a 404.
                try_files $uri $uri/ =404;
        }

        # pass PHP scripts to FastCGI server
        #
        location ~ \.php$ {
               include snippets/fastcgi-php.conf;
               fastcgi_pass unix:/var/run/php/php8.2-fpm.sock;
        }

        # deny access to .htaccess files, if Apache's document root
        # concurs with nginx's one
        #
        #location ~ /\.ht {
        #       deny all;
        #}
}


# Virtual Host configuration for example.com
#
# You can move that to a different file under sites-available/ and symlink that
# to sites-enabled/ to enable it.
#
#server {
#       listen 80;
#       listen [::]:80;
#
#       server_name example.com;
#
#       root /var/www/example.com;
#       index index.html;
#
#       location / {
#               try_files $uri $uri/ =404;
#       }
#}

server {

        # SSL configuration
        #
        # listen 443 ssl default_server;
        # listen [::]:443 ssl default_server;
        #
        # Note: You should disable gzip for SSL traffic.
        # See: https://bugs.debian.org/773332
        #
        # Read up on ssl_ciphers to ensure a secure configuration.
        # See: https://bugs.debian.org/765782
        #
        # Self signed certs generated by the ssl-cert package
        # Don't use them in a production server!
        #
        # include snippets/snakeoil.conf;

        root /var/www/html;

        # Add index.php to the list if you are using PHP
        index index.php index.html index.htm index.nginx-debian.html;
    server_name mychosenname.ddns.net; # managed by Certbot


        location / {
                # First attempt to serve request as file, then
                # as directory, then fall back to displaying a 404.
                try_files $uri $uri/ =404;
        }

        # pass PHP scripts to FastCGI server
        #
        location ~ \.php$ {
               include snippets/fastcgi-php.conf;
               fastcgi_pass unix:/var/run/php/php8.2-fpm.sock;
        }

        # deny access to .htaccess files, if Apache's document root
        # concurs with nginx's one
        #
        #location ~ /\.ht {
        #       deny all;
        #}


    listen [::]:443 ssl ipv6only=on; # managed by Certbot
    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/mychosenname.ddns.net/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/mychosenname.ddns.net/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot

}
server {
    if ($host = mychosenname.ddns.net) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


        listen 80 ;
        listen [::]:80 ;
    server_name mychosenname.ddns.net;
    return 404; # managed by Certbot


}

As already mentioned: This configuration does not interfere with my WordPress / Nginx when running without SSL at port 80, the installation is reachable from within and outside the network.

Thanks in advance!

Jens