I am not from Intel, but you may have received incorrect info about BIOS jumper. I do not recall details at this moment, but the instructions for NUC jumper are typically different from those of all previous/regular Intel motherboards. Regarding the two keyboards you tried, were both of them Microsoft? When I received my NUC, I was in similar situation to you because all I had were Microsoft keyboards. When I attached a non-Microsoft keyboard, I was able to use the keyboard. Then I updated BIOS, and after that I was able to use Microsoft keyboard. And what you may need to do for booting is to make sure that legacy boot is enabled (defaults may depend on the BIOS version).
Thanks for replying. I'm quite sure I am following the correct instructions about the jumper. There's a page dedicated to the NUC here
Neither of the keyboard are Microsoft.
I simply can't do anything with it, it is as though it was "bricked" right out of the box. Very disappointing.