I've tried getting this information out there as much as possible, but I'm not having a lot of luck actually getting an answer from anyone at Xbox whether or not its supposed to be officially supported or not. So, regardless of "official" support for it, heres how to get your Xbox One working with a USB keyboard (Wired or Wireless)
1. Turn off your xbox completely. Not Standby.
2. Plug in the USB keyboard cable or dongle (if wireless)
3. Turn on your console.
4. Voila.
5. Enjoy.
:)