With IPv4 scarcity, many carriers had to employ NAT (network address translation) so that many users are mapped behind a single IP at the same time. This of course makes impossible to put a personal server on a local home network because although connecting to external addresses is still doable, any incoming packet wouldn't know which one of the users it should reach without explicit rules that the users have no access to.
It also means you will frequently be blocked by services such as cloudflare if anyone else you're sharing an IP address with is infected with a spammy virus.
I’ve been behind CGNAT once. It was a miserable experience for this reason. (No idea how many people there were at the one IP address, but https://iknowwhatyoudownload.com/ reported on average ten or twenty hours of video per day being downloaded via BitTorrent from the address, none of which was from my endpoint.)
Carrier-grade NAT. Generally rolled out due to IPv4 exhaustion.
Under CGNAT Your router does not get an externally reachable IP address from your ISP, as it sits behind ISP-level NAT router that assigns addresses to subscribers much like your home router assigns addresses to your home machines.
So you can’t run any sort of externally reachable service at all.
Like... what ISP would go out of their way to do that? Call me cynical, but I doubt there's an ISP that uses CGNAT who would forward a port to you. Like, they all do the total absolute minimum necessary to get you Internet access. Why would they bother creating some way to let you forward a port to your computer? No average person needs to do that anymore now that everything is cloud-based. I could be way wrong on this, but I just have my doubts...