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/
Yes only. Note that I said “new ISPs”.
The older ISPs already own all IPv4 blocks, so while they can still give them out to private or professional customers, it would be stupid to sell the blocks to competitors.