I agree. GitHub is the biggest player, but it's a pretty layer on top of an inherently distributed system. If I get tired of Microsoft's shenanigans, I can pack up move to a competitor with only the normal amount of friction (like moving bug reports over, etc.). I use Gitea for my personal projects and it handles 95% of the code-hosting bits just as well.

I'm not so relaxed about how easy it will be to move to a new issue tracker.

When you're moving from a self-hosted system to a proprietary system, you can do the work yourself to make sure there are redirects from the old URLs to the new ones.

That option isn't likely to be available when you're moving the other way.

I observe that github is happy for you to "bring your own domain" for github pages, but AIUI issue and PR URLs are always under github.com .

Maintaining links is going to be a pain in the neck, sure. I don't mean to make light of it. However, that's kind of inherent with going from one service to another, and not something GitHub's doing to make it artificially harder.