OK, I think, Juergen’s answer brought some insight to you. This should answer the first question.
Regarding the second question: I was referring to e.g. https://www.mndm.pl/. This one uses a self-signed certificate at the moment.
What are you meaning by the SSH part? The SSH does not use SSL certificates as far as I know.
I do not know much of CentOS. But I assume there is a mod_http2 module to be installed.