I tried adding DeviceSupport per earlier suggestion and while Xcode can now attach & download the app to the device, debugging (e.g. setting breakpoints or viewing variable states, etc.) do not work so it can only help a little.
It is ridiculous for Apple to mandate an Xcode dot release update (12.5) to require a major OS release upgrade (from Catalina to Big Sur) and similarly for aXcode major release (12.x) to not being to support all major iOS 14.x releases. This force upgrade makes NO sense whatsoever. 😡