As a follow-up. The Apple Devs via the Feedback Assistant program have resolved this for me by getting me to run the following command in the terminal which deletes my Device details for debugging, to force Xcode to recreate them from scratch.  rm -r ~/Library/Developer/Xcode/iOS\ DeviceSupport

Thanks Vyacheslav, sorry to hear you are also having this issue, but its good to know I am not alone. I have logged a Feedback case and also a Technical Support request. Shall post here if I manage to resolve it.

Further testing overnight suggests this is an issue with the debugger. If I allow Xcode to build and run an app to one of my devices, it will launch and then freeze on a black screen. After a few minutes the app progresses to its main ContentView and the console appears to then function as normal. I am quite new at this so am a little lost for where to go to look for solutions. Cheers.