I have a Windows 10 - 32gig Dell 5820 with an AMD WX5100 8GB video card. When I connect to a 4K TV with a Display Port to HDMI 2.0 cable to the TV, the max resolution offered is 1920x1080.
When I connect my laptop exactly the same way, DP->HMDI with the same cable, I get higher resolution options, so it has to be settings on the card or Windows 10.
My laptop has an Intel Graphics 4600, Windows 10.
I updated the AMD drivers, but still only get 1920x1080 max option.