Surprise! It looks like NVIDIA has been quietly working on this feature, and has released it as beta with their 436.02 drivers.

The feature is only accessible with their latest GPUs, and carries additional restrictions:

• Requires a Turing GPU (GeForce RTX 20 series/GeForce GTX 16 series) and Windows 10 April 2018 Update and above
• Integer Scaling is not supported in Surround mode, on tiled displays, with custom resolutions or when DSR is enabled
• Pixel formats supported: RGB/YUV444/YUV422
• When the display has a different aspect ratio from the game, you will see black borders on the display.
• Integer Scaling is not supported in MSHybrid notebooks where the integrated graphics are managing the display properties

Now that Intel and NVIDIA are committed to supporting the feature, AMD will likely soon follow. Hopefully they will be able to make the feature backwards compatible with their previous generation hardware.