[fritsch]

But still the original issue remains, if I use this: "Xorg Full + Kodi Limited + TV Limited" the user interface is too dark. It's correct if I don't select limited range. Still video playback of black levels is correct with limited range selected. Is it possible to adjust just user interface brightness?

 No.     

Are skin graphics and colors correctly converter when limited range is used? Looks like if I manually edit graphic files to black = 16, then the skin starts to look normal again, only thumbnails are still too dark.
I didn't have this problem originally in Kodi, it started sometime last year. There were other posts about it during that time, I think the problem was never fixed (and not seen by all). 

 That's odd - cause the gui shader does this conversion already. Make sure if you toy with dirtyregion stuff, most of them make no sense anyways. When debugging such issue make sure that the complte viewport is always repainted - which is the default DR mode.If you want to save power use <gui><smartredraw>true</smartredraw></gui> instead