I see it mentioned very little but the #Gitea project is actually a very nice project to self-host if you want a git environment with issue tracker, admin interface etc. It is fast, light and easy to install and maintain.
We use it for varia for: https://git.vvvvvvaria.org
It was forked from #gogs in response to project governance issues: https://blog.gitea.io/2016/12/welcome-to-gitea/
What these projects could use is some form of federating comments/issues etc across servers.