Is it possible to create a workflow that submits the app to review? Not only TestFlight External testing, but submits the app to App Review in App Store Connect? So when the master branch is changed, the workflow starts and submits the new app version to review in App Store Connect
For that, I would suggest a custom script in ci_scripts / post script install using fastlane. https://developer.apple.com/documentation/xcode/writing-custom-build-scripts https://docs.fastlane.tools/actions/deliver/
you will still have to repopulate your details in the fastlane folder / metadata / screenshot / release note and commit. Plus you will need an API Key that you will pass as a secret in your env variable. Anyway you can test all the steps locale before using Xcode Cloud to valide.
Now the question, do you really want to do that? on my side I much prefer to control the release and not have auto submit unless you have like Netflix, or over big player, 2 weeks release cycle and in app release notes.