Fair point.

That said, I don’t think that works well in a single centralized forge today either. Usually you still need A to actually make a release with the fix, which isn’t tracked by the issue/PR system.

I'm not sure. On GitHub I see plenty of bug reports which say "this is broken" with references to other repos. Those backlins are useful when someone does figure out the fix.

That said, I'm very much in favour of people and projects moving away from GitHub.