It's working today, after I applied #4 from zack1001's post above - "Added the libswift_Concurrency.tbd in Link Binary with Libraries from Build Phases and set as optional." Thanks!

The same thing is happening to us today!! The app runs fine under Xcode on an iPad connected by wire to my MacBook. When we publish the app in TestFlight, it crashes immediately with the same missing library. We were also getting an automated email after each distribution on TestFlight: ITMS-90863: Apple silicon Macs support issue - The app links with libraries that are not present on Mac:     @rpath/libswift_Concurrency.dylib We were able to prevent these emails by navigating in AppStoreConnect to: App Store / Pricing and Availability / iPhone and iPad Apps on Apple Silicon Macs and un-checking "Make this app available"