HTTPS doesn't care about IP addresses. It's all based on domain names. You can get a certificate for any domain you own. You can also set said domain to resolve

HTTPS doesn't care about IP addresses. It's all based on domain names. You can get a certificate for any domain you own. You can also set said domain to resolve to any address you like, including a "local" one. NAT has rotted people's brains unfortunately. RFC 1918 is not really the way to tell if something is "local" or not. 25 years ago I had 4 publicly routable IPv4 addresses. All 4 of these were "local" to me despite also being publicly routable. An IP address is local if you can resolve it and don't have to communicate via a router. It seems too far gone, though. People seem unable to separate RFC 1918 from the concept of "local network".