Hello @wirytiox, welcome to the Let's Encrypt community. 
Only the HTTP-01 challenge of the Challenge Types - Let's Encrypt needs Port 80.
There are 2 other choices the DNS-01 challenge and the TLS-ALPN-01. Please read the Pros and Cons of each.
If you choose the DNS-01 challenge here is a list DNS providers who easily integrate with Let's Encrypt DNS validation
A list of some of the ACME Client Implementations - Let's Encrypt
There are other Free ACME CA Comparison - Posh-ACME
Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. crt.sh | example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
My domain is:
I ran this command:
It produced this output:
My web server is (include version):
The operating system my web server runs on is (include version):
My hosting provider, if applicable, is:
I can login to a root shell on my machine (yes or no, or I don't know):
I'm using a control panel to manage my site (no, or provide the name and version of the control panel):
The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot):
Thank you for assisting us in helping YOU!