Twigg
We've been building Twigg for quite a while now and open sourced all of it. Its goal is to provide a similar developer experience to the Google/Meta/Phabricator one. The project consists of not only the version control (the "Git" analogous) but also the software forge (the "GitHub" analogous) and the CI/CD server (the "GitHub actions" analogous). You can self host it or use our hosted instance (https://twigg.vc). Come check it out, and leave us a star on GitHub!