Not sure it helps but it's not a lot of trouble to have XCode 10.3 and XCode 11.x on your machine. Switching between involves xcode-select...
@borkdude Re: 100% CPU usage, make sure your Krell is latest. There was a bug a couple weeks ago that pegged CPU usage.
That works when you’re not on an old version of macOS. The issue he has is that his iOS is ahead of what his current Xcode supports