Try the following:
$ nslookup github.com
[...]
Non-authoritative answer:
Name: github.com
Address: 140.82.121.3
See also the completely ignored post in their forums.
It’s not generally a hardware problem. It’s a resourcing problem. Companies like GitHub will have complex software and architecture. IPv6 requires them to get a pool of IP addresses, come up with an IP address management strategy, make sure all hosts have IPv6 addresses meaning that now provisioning systems and tooling to management DNS has to plumb IPv6 addresses through too.
Then the software stack has to support it. Maybe their fraud detection or auditing systems have to now support IPv6 which means changes to API schemas.
None of this is a good reason why they shouldn’t do it, but I’ve had to make similar decisions at my job as a software engineer on what looks to be simple but actually requires changes across systems.
