Context:
People have been asking for IPv6 Support on GitHub since years (probably a decade by now)
... and someone even got so annoyed that they decided to setup a dedicated website for checking this: https://isgithubipv6.live/
China block much of the internet so who knows with china. Do not know if anyone have real china numbers of IPv6 deployment. They also had their own "IPv9" that was rumored some years ago that may or may not have been used internally.