Happened to me twice (a decade ago, though) that I had some niche project (one a serial terminal, another a laser cutter firmware) that was on github with users left but the maintainer long gone.

I was able to pull the graph and collect patches and bugfixes from forks, like from a fablab somewhere using the same hardware, pushing to their fork with all their other location-specific stuff. In one case I discovered like four different forks with a different fix for the same problem.

Now you could argue the "social" part wasn't working if people fixed the same issue multiple times without knowing about each other. But at least github made it possible for me to collect everything there is, review and merge it into my own repo, and then drop a comment at the original issue tracker. (Which would have gone 404 had it been self-hosted, or with registrations closed due to spam.) In both cases I eventually got feedback from other people who found my branch and used it.