To bump an old thread... UUID is now Sendable! https://developer.apple.com/documentation/foundation/uuid/

I have also seen this problem with xcrun altool for several days. Using Transporter worked about the problem for me (but is a bad workaround long term because it prevents scripting). I've submitted Feedback FB9742349 on this problem, please consider filing your own Feedbacks / Radars.

2 years later... I found a simple way to force an SKView to live resize on Mac; just make it think it's not live resizing and it won't halt the redraws: class LiveResizeSKView: SKView {     override public var inLiveResize: Bool {         get {             return false         }     } }