As far as I could tell, if you create a Main.swift file, you can't just open that in XCode and start running it as an iOS/macOS application, and instead have to create a .xcodeproj/.xcworkspace through XCode, and add your Swift to the scaffolded project - this seems backwards to me.
(I then separately complained at all the steps it took to get it running without XCode, as I didn't want to be locked into using it)
(I then separately complained at all the steps it took to get it running without XCode, as I didn't want to be locked into using it)