Okay, I'm a little more coherent. Netflix OFFICIALLY requires Intel SGX, which is on Kaby Lake or later. However, the Windows Fall Creator's Update appears to have enabled AMD hardware to support Netflix 4K. You will need current drivers though.
I'm in the process of updating my rx 480 drivers to see if my Skylake based system will support 4K Netflix - I have my doubts, but I'll report back.
Edit: Nope, an updated 480 does NOT get me 4K Netflix - oh, you will have to use the Edge browser to get your 4K as well. I can hit 1080p with my rx 480, but that's where I'm capped. Which is really stupid, given that the card is physically capable of all the requirements. I have seen people reporting that they get 4K Netflix with a Vega card - I suspect a 560 on up would do it for AMD too, but can't confirm it. Nvidia cards, once again I believe it's the 1050 and up, can do it. If I build a Ryzen based machine, I might try my 480 again, but my understanding is that if your card is supported, your processor doesn't have to be.