A couple of months ago there was a Windows Insider driver release from NVIDIA that enabled 4K Netflix support on select GeForce GTX 1000 series video cards. Previously, this feature was exclusively available on systems with Intel Kaby Lake or AMD Summit Ridge or Bristol Ridge CPUs due to silly hardware-level DRM restrictions.
TechPowerUp writes NVIDIA's recently released 384.76 WHQL driver brings support for 4K Netflix to the mainstream version of Windows 10. There are still some other restrictions though, and it only works with Edge or the Netflix app:
Reddit user aethervisor discovered that the Windows Store (UWP platform) app of Netflix could play back content at full 4K Ultra HD resolution on their machine with an older CPU and GeForce GTX 1080 graphics. New-generation CPUs had become a requirement for this to happen, besides the latest Windows 10 version, an HDCP 2.2-compliant 4K display (and no active secondary displays that don't satisfy HDCP 2.2), a powerful enough GPU, and either the UWP app or the Netflix website on Microsoft's Edge web-browser. NVIDIA struck down a big requirement that opens up Netflix 4K to a much wider user-base.
Curiously, this is the second hidden feature of the GeForce 384 series. Earlier this week, it was reported that NVIDIA has finally enabled DX12 support for the Fermi GPUs.