master branch in Azure Repos could be as simple as a few clicks. But if you have complex policies or permissions in place, it may be a little more work.
To rename your
master branch you have to create a new branch and then delete the old one:
If you're also using Azure Pipelines (which you should if you're also using Azure Repos), you may need to fix a few other things as well, they're essentially the same as the ones you'll need to fix when using Azure Pipelines together with GitHub.