OK thanks for the tip and yes I have some Unix/Linux background. I only learned so far that osmc does some things a bit different than other linux OS-es. Will try my luck with rc.local.
Adding ‘loadkeys be-latin1’ to rc.local works! So I have a good enough workaround for the time being.
When it comes to Belgian keyboards relatively to French keyboards … https://en.wikipedia.org/wiki/AZERTY#Differences_between_the_Belgian_and_French_layouts_of_the_AZERTY_keyboard
Please let me know if I can contribute on this BE mapping. Just leave me the details how to proceed if you can use some help.