UIApplication::setDelegate does not work with Qt 6.8.1 for iOS

An application, that calls UIApplication::setDelegate from iOS UIKit, unexpectedly shows a black screen with Qt 6.8.1 for iOS while it displays a Window QML with Qt 6.7.3 as expected.(see attached screenshots)

• The issue was reproduced on iPhone 13, iOS 17.5.1.

• Even with Qt 6.8.1, omitting the line calling UIApplication::setDelegate makes the application run as expected.

• Reproducer attached.