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".
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".