We are changing our system. We settled on git (but are open for alternatives) as long as we can selfhost it on our own machines.
Specs
Must have
- hosted on promise
- reliabile
- unlikely to be discontinued in the next >5 years
- for a group of at least 20 people
Plus
- gui / windows integration
I would go with Gitea or Forgejo (not sure how this is going to last) if you need a complete experience like a WebUI, issues, PR, roles and whatnot.
If you’re looking for just a git server then gitolite is very good and solid option. The cool thing about this one is that you create your repositories and add users using a repository inside the thing itself :).
Then you can use any Windows GUI you would like like Fork, SourceTree, your IDE etc…