I've actually been trying to find that out myself, but no luck so far.
Not sure at all but Intel NUC's are EOL anyway. But alone from the stiff price tag they had I would expect they could afford the ~10 cents for the ir receiver for every unit they sell (or sold).
Will any of the recommended hardware allow powering on and off via an MCE remote?
I use a MCE remote with my $28 amlogic tv box that has IR receiver build-in. But it does only work out of the box with the remote shipped together with the box. To have it work with my MCE remote I have a simple IR-Receiver/Blaster (esp based, ~$8) which will react on my commands send from the MCE and "translate" it so that my tv box acts accordingly to my wishes. Combined with this IR-Receiver/Blaster my MCE Remote is like on steroids - I can easily control various appliances like TV, AMP and other stuff. My home theater gets itself ready with only one click* on my remote (before I had 3 different remotes for that task)
*one click on the MCE remote actually plays/blasts a sequence of codes which triggers a wall socket (no standby power draw for the home theater appliances), switches on the screen, amp and libreelec box