This was unnecessarily annoying.
If you have a private GitHub repositories that you would like to hook up to a Git GUI, GitKraken would have been my primary choice but they need pro account for that to happen. However, SourceTree is free for Azure DevOps. BUT, its setup never seems to work somehow, it turned out to be related to bad URL in HTTPS setup.
For detail see this post:
TLDR: use “https://*username*.visualstudio.com” in the address field for BitBucket SourceTree instead of anything like https://dev.azure.com/*username* or whatever long URL you might have copied from Azure Devops portal.