If you have the August 13, 2024—KB5041580 update. You’re good.
Routers simply need to block incoming unestablished packets (all modern routers allow for this) to replicate NAT security without NAT translation. Then you just punch holes through on IP addresses and ports you want to run services on and be done with it.
Now, some home routers aren’t doing this by default, but they absolutely should be. That’s just router software designers being bad, not IPv6’s fault, and would get ironed out pretty quick if there was mass adoption and IPv4 became the secondary system.
To be clear, this is not a reason not to be adopting IPv6.
Routers simply need to block incoming unestablished packets
This is called a firewall
Yes, and no. A firewall is still a firewall if it is configured to have all ports open. The Linux kernel firewall is still active, even though its default configuration is, everything open.
My point is, for some reason there are some that are not configured to block incoming IPv6 by default. When that should be the standard home/consumer router default setting. Then the user can open ports to ips as they need them.