We've been pretty happy with Phabricator. Its code review is miles ahead of the others, in my opinion, and other parts also work well for us. Of course, it's

We've been pretty happy with Phabricator. Its code review is miles ahead of the others, in my opinion, and other parts also work well for us. Of course, it's not a direct replacement, since they don't have free, centralized service like GitHub/Lab does. But, it's 100% open source and you can easily host it on a potato.