since this and similar issues are still persistent, I am assuming that NUC support has been silently dropped.
Even LE 12 doesn't seem to understand the hdmi channels available on a NUC, 11 the number of which seem to increase every time I fail top playback something.
Interestingly, it used to work on le10, somewhat, since there you can also select the video out (not anymore on le11), but it has stopped now to the point that no hdmi audio is available at all. I don't know if the hardware is somehow rotting away, but I cannot convince myself to believe that.