You have to be careful, there are two separate cases for IR, only one defaults to RC6 MCE remote:
1. Board is suspended or in sleep mode. Power management firmware is in charge of IR. If board comes with IR remote (TV boxes only), power key on that IR remote wakes up board. If IR remote is not bundled with the board (all SBCs), then RC6 MCE power key is default (your case).
2. Board is running, e.g. Kodi. In this case, Linux is in charge of IR. Again, if board comes with IR remote, correct keymap should be already active. If not, there is no default, you have to set it up (your case).
Very clear as always. I can't do anything different than saying "Thank you!" for the umpteenth time! I can confirm that I can turn it on by the Dell RC6 remote. Now I need to do the rest following the guide I've already found and linked in my previous message.
Everything done! I've taken a look at that guide and by this command:
I've been able to sort it out. Now it works under both the scenarios. GREAT!
Just a bit more to learn, a bit more to tweak... The command above is absolutely fine but the changes aren't persistent: after a reboot or power down the remote stops working under Kodi.
I needed to create the file /storage/.config/autostart.sh with the following content:
Now EVERYTHING is exactly as I wanted to!