I’ll add the following Declare into the next version of the Android Design Extensions!
' Working for API 30+ (Android 11+)
If System.Version.BuildVersion.ToInteger >= 30 Then
Declare Sub ShowFullscreen Lib "Object:Screen1:MobileScreen" Alias "getWindow()!!.getDecorView().getWindowInsetsController()!!.hide(androidx.core.view.WindowInsetsCompat.Type.systemBars())"
ShowFullscreen
End if