A big thing with Github its the unified functionality across most of the OSS world - that we can search across all projects, leverage pipeline actions from other projects, and easily have a single dashboard for our own contributions and interests across all projects.
I'd hate to see a move to forge balkanization lose this functionality. But this would not be heavyweight data to federate. So are there any forges with a good story for federation?
There was some work to address this issue with federation in Gitea, but I haven't kept up with how well that went. Our practical solution was to just mirror our Gitea repos into GitHub. That way they're discoverable, releases can be downloaded, and so on. Not a perfect solution because users get confused as to why they can't open issues, etc.