How many people use Github for discovery though? I usually find interesting projects through a search engine, through word of mouth, through posts on here, etc. at which point it doesn’t really matter where the repo is hosted. A lot of the useful projects I use aren’t even on Github.
As far as I know, Gitea is current working on federation support, which will be great. It’d be like Lemmy where you can browse repos, submit issues, etc from one instance even if the repo is hosted at a different one. Git was really designed for a model like that, not for a centralized one.