Xcode 12 4 Unsupported OS version after iPhone iOS update 14 7

Question

Following an iOS 14.7+ update, Xcode 12.4 is no longer able to develop for that iPhone model.

The most recent iPhone will have alongside it when selecting a Build Destination in Xcode (Product > Destination > [device] or from the UI menu shown below:-

(unsupported OS version):

iPhone listed with "(unsupported OS version)".

Big Sur and Xcode 12.5 upgrades are not possible.
I can't upgrade to Xcode 12.5 since I'm stuck on Mac OS Catalina (ancient hardware) and it needs Big Sur.

How may device support be added to or updated in Xcode so that we can develop for an unsupported iPhone version (iOS 14.7+)?

Answer 1

This may only be a short-term fix, but this is what I found to work:

Access Device Support by going to contents/Developer/platform/iPhoneOS.platform.
Copy the device support file from your previous iOS 14.5 or an earlier version.
Copy, then paste, changing the iOS number to 14.6.
You should be able to run your code on your phone after restarting Xcode.
In case someone gets stuck or can't run Xcode on their phone, FYI this has worked for me previously also with a different iOS, so it could be able to help for later versions.