Xcode stuck on copying cache files from device tvOS
Had this issue with iPhone SE, rather than AppleTV, and found only this question in my searches.
Ended up that I simply had to wait (very impatiently) with Xcode active on my Mac screen, and keeping the iPhone awake/unlocked, for it to finish. Felt like forever, but it was less than 30 minutes in the end.
It seemed to stop the process if I moved off of Xcode to work on something else, or if the iPhone screen locked. So, keeping Xcode as the active app and keeping the iPhone awake seemed to allow the process to finally finish.