I can't get past double clicking on any project in the repository browser window after installing macOS 12.3 and Xcode 13.3. I have three versions of Xcode available, 13., 13.2.1 and 13.3, and have alternatively selected the command line tools for each one in trying to find a combination that doesn't crash (the repo browser window for sourcetree closes immediately and the app is no longer running). I've also tried in turn to run sourcetree versions 4.1.3 through 4.1.6; they each crash in the same fashion.
When I first started sourcetree, I was running Xcode 13.3, but sourcetree apparently started to verify Xcode 13.2.1. Not sure what's up with that.
I also rebooted macOS 12.3 to see if that would change anything.
It appears to not matter which project I select to open.
Switching from internal to system git has no obvious effect.