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 … AZERTY - Wikipedia
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.