Xcode 11 Beta 5 - Loading a plug-in failed
I was able to get my SwiftUI project running on Catalina beta 4 with Xcode beta 5. I too got the warning mentioned by OP.
And as mentioned in comments, the only negative impact I've seen is being unable to use the preview canvas. Other than that, everything else in my project is running well. Just using the simulator more ;)
this will get rid of the error message but will not bring canvas back.
based on:https://forums.developer.apple.com/thread/120614
Please go to: /Applications/Xcode-beta.app/Contents/PlugIns/UVKit.framework and delete all the shortcut files in all folders of UVKit.framework (Be sure DONOT delete orginal files).