alt Hacker NewsIPv4 has exact same problem, the NAT is working here because devices does not actually have proper Internet connection, all connections are terminated on NAT and reassembled after.
Actual solution could be extending TCP and UDP or make a new transport layer procotol that handles changing addresses, similar to what QUIC do. But we cannot do it exactly because things like NATs existing, thus QUIC build was build on ossificated UDP. Imagine if instead of IP+port a connection use unique per-connection hash to persist IP addreses changing. No more trying fighting to keep the IP the same.
Ipv4 does NOT have this problem. The typical setup is always NAT for ipv4 lan, so external address can be changed with minimal disruption.
All ipv4 apps that require hole punching assume they will need to "discover" the external address anyways, for every new p2p connection.
In contrast to the vast majority of ipv6 apps which assume their ipv6 address is identical to external ipv6 address, as this is(was) the main marketing point of ipv6 - directly addressable end points.