That may be useful if you buy a certificate. Letsencrypt uses another solution.
So start with some basics:
Then select a client.
Then answer all of the questions of the standard template.
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. https://crt.sh/?q=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):
Question: why would you want your printers to have a certificate from a publicly trusted certificate authority?
I’m hoping they aren’t accessible from the outside world? Which also presents a very likely issue with you trying to use Let’s Encrypt certificates (or publicly trusted CA certificates in general): the hostname has to be accessible or resolvable from the world wide web. So a hostname from a domain like example.local won’t work at all.
You can do this with various client applications, such as some of those that @JuergenAuer mentioned, but as @Osiris mentioned, it’s only relevant if your printers have a public domain name, because those are the only names for which Let’s Encrypt is allowed to issue certificates.
In general, you will probably not have a very good experience using Let’s Encrypt for this application because Let’s Encrypt is intended to be used with automated integrations. Unless your printers themselves contain logic to interact with Let’s Encrypt, it may be difficult to automate the integration. In that case, you may be stuck doing very frequent manual certificate renewals, since Let’s Encrypt certificates have a deliberately short lifetime.