I don't use Google AdMob, so for sure it is not related to the problem. If I comment it out or I use instead the old API @Environment(.presentationMode) var presentationMode then the issue is not present.

@Peter_Schorn I tried but on iOS 15 if I conform explicitly to ViewModifer and Animatable an animation doesn't work at all. If I conform to AnimatableModifier then it somehow works. On the other hand, if I conform to AnimatableModifier then on iOS 13.0 the app crashes (cannot find probably the protocol in SwiftUI framework - probably a bug).