According to this link:
https://stackoverflow.com/questions/69418845/app-tracking-transparency-dialog-does-not-appear-on-ios
RequestAuthorizationTracking should be called in:
applicationDidBecomeActive()
(according to El Tomato in that thread.)
Especially for iOS 15+. But in Unity the closest method is
public void OnApplicationFocus(bool focus)
But this is not called when the app starts up on a real iOS device and the iOS Simulator, only when it goes to background and then foreground again.
So where should this code go:
ATTrackingStatusBinding.RequestAuthorizationTracking(this.DidCompleteAuthorizationTracking)