NUC6CAYH Libreelec installed. TV is Panasonic TX-50DX700B. I find that I can navigate around many of Libreelec's menu's using the TV remote. If I turn the TV off it puts the NUC into standby. Turn the TV back on and the NUC stays asleep. Have the NUC turned on, turn the TV off at the wall socket, hit the power button on the TV remote and the NUC goes into standby proving it is an IR clash and not some weird HDMI thing happening. Go into the NUC's BIOS and disable the CIR and it is unaffected by the TV remote.
I've posted this just to save anybody else with the same set up tearing their hair out wondering what's going on. It's fun altering the TV's volume and watching the NUC's volume change at the same time.