Unfortunately this suffers from compounded niche-ness. Even with huge interest and constant public f-ups from social media companies, the Fediverse has failed to gain any real traction (likely due to the unintuitiveness of cross-server identity).
GitHub is already niche for the general populace, most people haven’t heard of it. Among programmers, alternative SCM platforms outside of GitLab and Perforce are niche. When we multiply the two together we get an incredibly small set of potential users (and the UX challenges of ActivityPub are still there).
This doesn't compound though - are we trying to get the general populace who doesn't use GitHub to use something that supports ForgeFed/ActivityPub?
On the other hand, it seems significantly easier - instead of trying to convert the general populace to ActivityPub, we're trying to convert technically literate developers and related peoples to use ActivityPub.
Also, for what it's worth, I quite enjoy my self-hosted Mastodon account and long since stopped using Twitter and Facebook.
ActivityPub does not address or solve the problem of discoverability, which is what the parent comment is talking about. So it's not a solution to that problem.
