That was a clever idea, thanks! Did the same and now I was able to remove the self managed provider from the integrations. Now I finally can start over and try to get our self-managed gitlab working with Xcode Cloud.

For me that is the problem. In App Store connect there is no Xcode Cloud integration, it's only showing the get started with Xcode Cloud message. So there is no way to Deregister. When I try to setup a workflow from Xcode I am directly being redirected to step 2 of the Grant access flow. So I am wondering if there is a way to start over and how to do this. Thanks!