Soldato
I believe the App is capable of UHD but I'm not 100% sure. Of course it would need to be on a UHD capable device like a newer 1TB Q box or an older 2TB, with the UHD subscription.
I have the older 2tb box with a 4k tv and it defaults to HD. My Qbox has output set to 2160p 10bit. I guess it could be throttled due to the current bandwidth rules.