I think you can do this:
- Go to https://www.unique-local-ipv6.com/ and get a random ULA prefix.
- Create an IPv6 pool with that random prefix.
- Add an IPv6 address entry to the “dockers” bridge interface, using that ULA pool (similar to how you added the address entry to “Local Bridge” using the "IPv6_Pool). This will add the necessary IPv6 routes.
- The IPv6 address of the router on that “dockers” bridge (with the ULA prefix) is now the gateway that you use on veth1, similar to how 172.16.0.1 (which is the IPv4 address of the router on “dockers”) is used as IPv4 gateway.
- You assign the IPv6 address to the container (similar to 172.17.0.2) but the address is an ULA address with the first 64bit is the 64bit prefix that you assigned to the “dockers” bridge, the 64bit at the end (the interface ID) you can choose whatever, maybe ::2 to be short, with /64 as prefix length.