Issues, releases, CI, docs, security advisories, search and discoverability all tend to get coupled to GitHub over time.
For open-source projects, I like the idea of self-hosted as the source of truth, but still keeping a read-only GitHub mirror so people can actually find it.
We let Microsoft parasitize our brains with this. The software community has long had alternate forums. GitHub isn't even a particularly good one, and it's recently just become a swamp of generated content, fake stars, and mining your content.
In the last couple months at least once a week I get some LLM generated phishing spam from some bot that "found your projects on GitHub and want to collaborate" etc.
And it's well documented now how you can just go out and "buy" GitHub stars.
Please. Cut the umbilical.
I think trying to re-host git itself might be more trouble than its worth. My kingdom for someone to build this so I don't have to use ADO boards anymore.
One issue is that issues tend to be monotonically increasing numbers, and references to old issues vs. new issues get confusing over time.