You could just make a CA cert and sign a domain name that you always point to some RFC1918 non routing address. I’ve never done this because I try to avoid thin

You could just make a CA cert and sign a domain name that you always point to some RFC1918 non routing address. I’ve never done this because I try to avoid things that “require https even with localhost” but I’m fairly certain that would work and all you need is the OpenSSL command.