Some of the keyboards and mouse devices that have been officially validated can be found here; Tested Peripherals for Intel® NUC Kits NUC5CPYH/NUC5PPYH.
Regarding the issue you are reporting I would like to know if have tested any Windows version, and I would also like to know what is your BIOS version.
Before you are buying a new keyboard try the following:
1. Connect Logitech Unifying Receiver on USB extender cable in order to move it a way from NUC USB3 port (this will reduce the RF interference)
2. Download Logitech Unifying Software: Unifying Software - Logitech Support . Install an run this software. Depress Advanced button and update keyboard firmware to the latest version.
Hope this will help
I was thinking it might be a BIOS issue. At the bottom right corner it says "Visual BIOS 2.2.20" So I don't know if that is the latest version or not. Does 2.2.20 sound right? Or should I try upgrading? I also have the Linux setting checked in the BIOS. Testing Windows is the next thing on my list. I also have the Intel Ubuntu 16.10 video drivers installed as well. But I know Intel doesn't officially support Linux, so it may ultimately just be an issue that comes down to that.
Thanks for the reply Leon. Unfortunately Logitech didn't make a Linux version for those drivers D: But I appreciate the input anyways!