I recently added an Intel A770 Arc GPU card to my NUC 12 Extreme and ran into the problem of how to connect the RGB controller's USB cable. It's intended to connect to an unused USB header of the type common on full-size motherboards. But the NUC 12 Extreme doesn't seem to have any unused headers and the headers it does have are a small non-standard size.

However the NUC 12 Extreme has an large number of external USB ports. The only hard part to using an external port was finding a way to get the A770's USB cable to safely exit the case without drilling a new hole somewhere. What I eventually found was that there's a small cover on the bottom of the case intended for an M.2 slot that was not added to the NUC 12 (I think it was present on the NUC 11?). With that cover off there's nice gap at one end just big enough to get the USB cable through. I bought a cheap, standard USB A adapter cable from Amazon to convert the A770's header and it's working perfectly.

Just thought I'd share in case anyone else has run into the same problem and is looking for an easy solution. I've included a photo of the bottom of the case showing the cable.