Screen Mirroring on iOS does not work in Avalonia 12

[freddiesmartbox]

Describe the bug

When mirroring the iPad screen to either a Windows or OSX device, Avalonia applications initially show a Splash Screen correctly on both displays, but once the application itself loads the device screen goes white, but the mirrored screen shows the application running normally (Animations are running, so we know it hasn't locked up); no touch input appears to be received by the application from the iOS device.

We have - on a more complex application - briefly seen the application appear on the iPad screen immediately after the splash screen before it goes white.

To Reproduce

Scaffold a dotnet new avalonia.xplat
Run the iOS application on an iPad (we have specifically been testing with an iPad Mini 17 Pro running iPadOS 26.4.2, but we have reports from other devices)
Enable AirPlay on the Mac/Run Reflector 4 on Windows
Mirror from the iPad to the Mac/Windows device
Run the application: the SplashScreen will show, but once the application loads the iPad display will go white/blank and touch input will do nothing

Expected behavior

In a default configuration, the appearance of the application should be identical between the device screen and mirrored screen.

Avalonia version

12.x

OS

iOS

Additional context

We've tested with both our own application and a dotnet new avalonia.xplat on 11.3.7 and 11.3.18 where it works as expected, and 12.0.5 and 12.1.0 where the problem presents.

When testing mirroring to a Windows device, we using Reflector 4; to OSX we are using built in screen mirroring functionality.

We do not see the problem when using QuickTime player to record a movie with the iPad plugged in over USB.

[freddiesmartbox]

One of our devs did some investigation and concluded this was likely due to the AvaloniaSceneDelegate changes to support the 'modern' lifecycle management since iOS 23 and required for iOS 27 and its interactions with SingleViewLifetime: as far as we can tell, what is happening is that the application is loading normally, and then WillConnect is called when mirroring, which calls InitWindow, which swaps out the View in the SingleViewLifetime, which then moves its _mainView over to the new Scene: the result is that the original scene has no control.

Having finally got a debugger working, we can see that the MainView is indeed being re-attached when mirroring starts.

Another random observation is that starting an application normally and then mirroring also presents the reported behaviour, so it's not some weird a start-up issue (all consistent with the above)

This is all a tad worrying, because based on the plist files there's no indication that any of this should be happening, and I'd hope/expect that iOS would be falling back to a pixel-copy approach for the applications as is presumably what happens with the screen recording with QuickTime.