What corporation are you talking about? Have you never heard of someone self hosting software for their family and friends? You know, an intranet.

Just buy a domain and use dns verification to get real certs for whatever internal addresses you want to serve? Caddy will trivially go get certs for you with one line of config

Or cheat and use tailscale to do the whole thing.

Self hosting doesn’t usually apply connecting on a private network usually.