That's exactly what I did, and it fixed the compilation problems. But to make sure what I'm fixing for iOS15 doesn't break iOS14, I installed iOS14.5 runtime in Xcode 13, and that's where the problem occurs. I can successfully compile the app, but at runtime, the 14.5 simulator crashes with: dyld: Library not loaded: /System/Library/Frameworks/_CoreData_CloudKit.framework/_CoreData_CloudKit   Referenced from: /Users/andrei/Library/Developer/CoreSimulator/Devices/8554B734-4894-4DD0-A8FA-6C20983F3A49/data/Containers/Bundle/Application/29E251FD-B330-4B30-B3B8-22A86C2961A8/XXX.app/XXX   Reason: image not found (lldb)

Has anyone found a solution here? or the root cause of the problem? This thread was initially commented by a "Frameworks Engineer" and then left unanswered with multiple people having the same problem.

Yes. log bundle build artifact uploaded. FB14091724

Found the problem: It's due to `SWIFT_OBJC_INTEROP_MODE = objcxx