Comment by mrsssnake

Not really, look at a great post on Tailscale blog how such P2P connection can be established: https://tailscale.com/blog/how-nat-traversal-works

With IPv6 you might have to use a hack to make firewall allow incoming packets (like sending a dummy UDP packet to the peer first). The firewall only read, allow or deny these packets. While NAT must mess with the message IP//TCP//UDP headers to work.