ForgeFed is an ActivityPub Extension to allow cross-forge (git server) issues, pull requests etc. without having to create an account on each server. Forgejo (a Gitea soft-fork) is actively working on this integration.
Having this feature would be very useful. Many big open source projects run their own gitlab instance, which add extra frictions for contributing because you need yet another gitlab account just for those projects.
My experience with contributing to gitlab has actually not been as you describe. Fairly fast responses, obviously targeted releases so I knew when to try and finish any Mr adjustments, bots that provided excellent aid and even ability to ask for subsystem specialist help, when CI shot out confusing errors that appeared unrelated. Frankly, I was impressed. I understand not every feature or bug would go this way, but if you follow their guidelines, get product road map positioning, it works. The amount of commits going in to main are incredible. The number of MRs they handle is equally impressive.
All of that said, I've still got issues in gitlab that are seven+ years old, without any movement. But I get it that they have to prioritize and contributions are a different story.
GitLab don't have the monetary incentive to implement federation. Most of their revenue is coming from big companies which are mostly using private GitLab instance and won't want their projects federated.
That being said, hope this changes can get merge as somebody already done the dirty work for them. The beauty of open source.
How can more instances not lead to more money? Look at the explosion of mastodon and other federated software. There's a lot of good will in the community and being a viable competitor to Github is definitely not worth nothing. If Gitlab could offload the majority of users from their main instance, I bet it would actually save them money. And more users, probably also means more contributors since they'll have experience hosting the instance and fixing issues they run into.
IMO, it's short-term thinking to say "federation is of no value to us".
He presented the issue with gitlab very well. Setting up an entire new account is the major reason (besides time) I don't contribute to projects on other gitlab instances. For some reason Gitlab management didn't think it important at all (maybe even considered it a feature).
Their documentation has been frustratingly outdated at times too. But since GitHub is MS owned there are better options. I prefer codeberg for having an actual account on.