If you are looking at keeping track of who's working on what and how much your individual developers are contributing to your endproduct, you can try https://gitential.com/ , which is a software development analytics tool for all git-based repositories. Works with Github, gitlab, bitbucket, or vsts. And can be deployed on-premise as well!
As far as I’ve been able to tell, source tree has been completely abandoned. There’s a bug where if you have pipelines enabled on your repo, sourcetree will idle at 100% cpu on the Mac. That issue has been open for YEARS.
The only resolution is to use a different client.
I downloaded “git-fork” app about a year and a half ago and haven’t looked back.