That tutorial is for running on the same server via unix socket. Is there also configuration for running the reverse proxy on a different system with different port? I think it should be since this case might occur more often. On the other host I already have a certificate.
Just to be clear: This setup is for testing only. In production it will run on port 443, but for development and testing a VM at home is completly sufficient and saves the cost for renting a server in the meantime.