в OnCreate вот такую штуку прописал
if (Build.VERSION.SdkInt >= BuildVersionCodes.Kitkat)
{
// for covering the full screen in android..
Window.SetFlags(WindowManagerFlags.LayoutNoLimits, WindowManagerFlags.LayoutNoLimits);
// clear FLAG_TRANSLUCENT_STATUS flag:
Window.ClearFlags(WindowManagerFlags.TranslucentStatus);
Window.SetStatusBarColor(Android.Graphics.Color.Transparent);
}
https://stackoverflow.com/questions/46600003/fully-transparent-status-bar-using-xamarin