I have a NU8000 series TV that I am using as a PC monitor. My graphics card is a RTX 2080 Ti so I SHOULD be able to turn on UHD Color and get 4k 60hz Chroma 4:4:4 display.
But when I turn it on I get a black screen. The Nvidia controller won't let me turn on 4k 60hz 444, but maybe that's because the UHD color isn't turned on through the TV? But as I said when I turn it on I get a black screen so I seem limited to 420.
FYI If I tune down the resolution to 1080p and 30hz the Nvidia Control Center will give me the option to display in 444, but I still get a black screen when I turn on UHD color.
More FYI, when I run the signal through an "upsampling" Denon RS-X2400 then it does swap into UHD mode (automatically).