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/
Thanks for the comment. Kinda confirms my approach (mostly out of laziness) of "I'll do it when the ISP starts pushing it" is the correct one.
I think tech advocacy generally doesn't work, and in the case of IPv6 I can't see it working at all unless they can convince the ISPs to devote a lot more resources to it. But since I'm not an ISP... meh, whatever I guess.