It’s Fediverser. Yes, it is on github. Yes, I’ve posted about it, quite a bit.
I asked prolific users to join, I offered help to admins to set it up. I even offered the topic-specific instances to the wider community. None of these efforts were well received.
Github’s dominance comes from the network effects. Everyone’s on github, so if you have your project on a different repo, you won’t get as many visibility. If your project is on gitlab only and someone wants to report a bug, they need to:
A Federated forge solves all of that.