Your goalpost already moved from "IPv6 just works" to "IPv6-only just works" though. ;)
In all seriousness, I have IPv6 enabled and GitHub works just fine for me. Though at a slower speed sometimes because the IPv4 CGNAT is heavily congested in my area.
Presumably, they were working before Microsoft came up and they needed to be embraced, extended and extinguished.
https://en.wikipedia.org/wiki/Embrace,_extend,_and_extinguis...
Your goalpost already moved from "IPv6 just works" to "IPv6-only just works" though. ;)
In all seriousness, I have IPv6 enabled and GitHub works just fine for me. Though at a slower speed sometimes because the IPv4 CGNAT is heavily congested in my area.
If you count that as IPv6 just working, sure.