[mountainhill2]

Okay. Kodi is doing multi channel for the dvd you play. As well as the other AC3 5.1 Stream this is expected on kodi side. Kodi reopens the device more than three times (switching from menu to dvd and back, etc.) Nothing on your AVR display changes? It should.

For menu sounds, e.g.kodi is in the menus, kodi only outputs fl,fr. Do you also see multi channel when kodi is in the menus?

Yes, it's multi-channel PCM all the time shown in my AVR.

The DVD I was playing have 3 soundtracks, AC3 Stereo, AC3 5.1, DTS 5.1. 
I cycled through all of them when creating the debug log.
When it was playing AC3 Stereo, it output through all speakers (well, the sound was rather faint for the center channel, but it definitely output to the other 4.1).

Do you think it is really AVR-specific?
That I was "lucky" having this AVR?
I mean, LPCM is to me better than DD+ re-encode.

Question: does Resampling Quality have impact on these types of audio (which is already 44.1 or 48 KHz)?