I have libreelec installed on intel mainboard dg45fc.
It was connected to simple 2.1 speakers and worked fine. Now I want to connect it to 5.1 system. Unfortunately - rear speakers do not speak (so, they are no-speakers 
)
Mainboard has 5 jack connectors:
- rear (black)
- center/subwoofer (yellow)
- side surround/line in (blue)
- line out (green)
- mic in (pink)
All goes to subwoofer, which has final speaker connected to it.
And... there is no rear speakers in config. amixer don't show them, volume settings addon in kodi also.
They are completely silent
So...
Tried from other side: I have boot the machine from linux mint with the same effect: no rear speakers sound, no its settings. But using gui sound preferences, I can run 5.1 audio profile and rear speakers start to work (so, hardware is ok).
I guess alsa cannot handle my hardware but linux mint can use pulseaudio effectively and get the speakers to work.
Is it possible to switch libreelec/kodi fully to pulseaudio? How? Will that work well?
hmmm... there is workaround. I've connected my rear speakers to side surround (blue) instead of rear (black) and I have some sound there, but... it does not look well I expect rear speakers connected to rear socket...