I don't know how you've not encountered a 504 yet if you're actively using Codeberg. It's a known issue with a lot of impact.
GitLab's CI might be better but otherwise, the interface is pretty horrible and no one I know wants to have anything to do with it. I understand that can be subjective but everyone I've suggested it to in the past has come back with the same thoughts.
I remember trying radicle in its early days and having issues. Hopefully by now they've been resolved. Will check them out again.
I'm not a professor but I'm asked often for advice by students. Both due to open source contributions and also due to friends.