The problem is that any kind of automatic code change process like CI, PRs, code review, deployments, etc etc are based on having a central git server. Even security may be based on SSO roles synced to GH allowing access to certain repos.

A self-hosted git server is trivial. Making sure everything built on top of that is able to fallback to that is not. Especially when GH has so many integrations out of the box

Forgejo has all of the features you mentioned and is completely open source!