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/
You can subnet it with the exact same rulea as IPv4, nothing is chaning there.
Replace, for example, 192.168. with fd01::, with digits after this being divided however you like. You might step upon a too basic router that has it's own way to assign addresses with no way to change it, but that would not be IPv6 fault.