I used johntmcintosh solution, thanks! FYI, the package doesn't actually need to be complete. I get away with creating an empty tmp Package.swift file in my active dir.

Still seeing in Xcode 12.0.1. Tried adding SwiftUI as an explicit dependency marked 'Do Not Embed', but see the same. dyld: Symbol not found: _$s7SwiftUI12ProgressViewVyxq_GAA0D0AAMc   Referenced from: /private/var/containers/Bundle/Application/E9FB9FBD-F564-4236-B208-84CC14E96629/SwiftUIStylingProto.app/SwiftUIStylingProto   Expected in: /System/Library/Frameworks/SwiftUI.framework/SwiftUI  in /private/var/containers/Bundle/Application/E9FB9FBD-F564-4236-B208-84CC14E96629/SwiftUIStylingProto.app/SwiftUIStylingProto dyld: launch, loading dependent libraries DYLD_LIBRARY_PATH=/usr/lib/system/introspection DYLD_INSERT_LIBRARIES=/Developer/usr/lib/libBacktraceRecording.dylib:/Developer/usr/lib/libMainThreadChecker.dylib:/Developer/Library/PrivateFrameworks/DTDDISupport.framework/libViewDebuggerSupport.dylib