Many thanks for your comprehensive explanation, it's clear for me now. After spending lots of hours checking different LE versions, I realized that the only one that works for me is the 9.0 that I already have installed in the past.
I know it's because I use old hardware (Odroid-C2) but as I only use Kodi for films and series is enough for me. I installed the The Movie Database Phyton add-on and in this way I can continue download films information.
And yes, you're right, after checking with MediaInfo I have seen that all the "problematic" films are HEVC.