[TimoJ]

 Depends on many things: hw decoder, Xorg color setting and so on ...     

Is it possible to use xorg.conf to enable limited range with Intel graphics? I found messages that indicate it's not available for Intel.

I tried command line with xrand and it worked, now GUI is at the correct brightness (I hope...). I just haven't got it to work inside autostart.sh, not sure why it's not working.

But now I'm confused why I need to use xrand to get the correct brightness. Why there is no LibreELEC GUI setting for it? Kodi's setting effect only Kodi's part, not the underlying Xorg parts? Or am I missing something?   

 Please check kodi's wiki. I documented this some years ago, cause it is not trivial. In short only  the following settings make sense:

1) Xorg Full + Kodi Limited + TV Limited
2) Xorg Limited 16:235 (this scales(!)) + Kodi Full + TV Limited
3) Xorg Full + Kodi Full + TV Full  

Thanks, I'll check the Wiki. I think you mean this page: https://kodi.wiki/view/Video_levels_and_color_space
Looks like xrand limited is not the correct one, picture loses contrast or something. I think my TV is fixed to limited, there is no setting for it.