How to overcome Invalid Signature. Code failed to satisfy specified code requirement(s) in Xcode Cloud?

First of all, whenever I archive and upload to the App Store, it's working perfectly. No error, no warning. Just works.

But whenever I try to use Xcode Cloud with a standard workflow. I'm getting this error 5 times, one for my app, 4 more for every extension I have.

Invalid Signature. Code failed to satisfy specified code requirement(s). The file at path “PhoneDetox.app/Extensions/ReportExtension.appex/ReportExtension” is not properly signed. Make sure you have signed your application with a distribution certificate, not an ad hoc certificate or a development certificate. Verify that the code signing settings in Xcode are correct at the target level (which override any values at the project level). Additionally, make sure the bundle you are uploading was built using a Release target in Xcode, not a Simulator target. If you are certain your code signing settings are correct, choose “Clean All” in Xcode, delete the “build” directory in the Finder, and rebuild your release target. For more information, please consult https://developer.apple.com/support/code-signing.

I have a development team, I have automatic signing enabled.

• I have tried deleting Xcode Cloud data once.
• I have tried deleting all the certificates twice.

How can I fix this?

According to this Reddit post, it might be caused by having a non-ASCII character in your account name (which is the case for me; I'm using a German "Umlaut").

I've contacted Apple Developer support on this but haven't yet received an answer or discovered any workaround.