I want Xcode to stop downloading the files in
~/Library/Developer/Xcode/iOS DeviceSupport/12.4 where 12.4 is the iOS version of my iPhone. I have deleted them a couple of times now.
I also want to be able to connect my iPhone via USB to the Mac, without the fear of 2.5 GB bandwidth and storage cost.
This setting in Xcode Preferences → Components doesn't list 12.4.
Xcode 10.3, iOS 12.4, macOS 10.14.
These posts talk about removal only: