Failed reachability for IPv6

Or, to give all the credit to ChatGPT, it wrote my question with some more info:

Hi all,
I’m running NextBox on a Raspberry Pi behind a Fritz!Box router. I’ve configured:

  • Fritz!Box to allow IPv6 and IPv4 traffic on ports 80 and 443 (both directions)
  • DNS via deSEC, with proper A and AAAA records pointing to my public IPs
  • My Pi has a public IPv6 address, and ping6 google.com works fine
  • dig AAAA my.domain.tld resolves correctly
  • curl -6 https://my.domain.tld fails
  • ip6tables shows empty (no blocking)
  • Docker containers (including NextBox) are only listening on IPv4:
  • 0.0.0.0:80->80/tcp, 0.0.0.0:443->443/tcp
  • docker network inspect bridge shows “EnableIPv6”: true, but no IPv6 addresses

Since I’m using the default NextBox setup, I don’t want to manually recreate containers or break the integration with nextbox-daemon. I’d like to know:

How can I enable full IPv6 support for NextBox so that it listens on [::]:80 and [::]:443?

Is there a safe, NextBox-supported way to do this without manually overriding the container?

If not, is it acceptable to use a workaround like socat or nginx on the host to forward incoming IPv6 traffic to IPv4 (127.0.0.1:443)?