Enabling IPv6 in Docker

As others have said, you will need IPv4 to reach some services, NAT64/DNS64 at the edge could work for that.

Also, embedded system support for IPv6 is iffy. I know at some point Rokus wouldn't use IPv6 if IPv4 is present, if that's still the case, it may be that they won't use IPv6 even if that's the only thing available.

No, sadly not. There are plenty of sites that are not reachable via IPv6 yet. github for example does not work over ipv6.

At this point most home networks should already be dual stack v4/v6, and most up-to-date consumer operating systems are already doing "Happy Eyeballs" by default, doing DNS requests for both IPv4 and IPv6 at the same time and trying to use whichever returns fastest (and somewhat favoring IPv6).

Indeed, you can do that. I am actually doing that at various places at the moment. If you want to discuss how to do it, you can reach me directly on https://IPv6.chat

In my personal experience at home using Archlinux, IPv6 worked out of the box. I did once have an issue connecting to wiki.archlinux.org via IPv6, but that's about it. It just works transparently.