[Newbie_from_NJ]

You'll want to change this one: "Passthrough output device => ALSA: AML-AUGESOUND, HDMI" to the multichannel LPCM option there. If you don't see it, you need to update your CoreELEC to the latest stable build (v9.2.1). This way you'll get proper multichannel output also with FLAC, AAC etc. sources that cannot be bitstreamed.

I currently have CoreELEC Nightly_20191230. The only two options I show under Settings/System/Audio/Audio Passthrough/Passthrough output device: 

1. ALSA:AML-AUGESOUND,S/PDIF
   
2. ALSA:AML-AUGESOUND,HDMI
   

If I choose option number 1 (S/PDIF), then I lose the options to enable Dobly (AC3, E-AC3), DTS, TrueHD and DTS-HD. So this can't be it. 

Did you happen to mean #3 from this one instead:  Settings/System/Audio/Audio Decoder/Audio output device:

1. ALSA: Default (AML-AUGESOUND Analog), PCM
   
2. ALSA: AML-AUGESOUND, PCM
   
3. ALSA: AML-AUGESOUND, HDMI Multi Ch PCM
   
4. ALSA: AML-AUGESOUND, S/PDIF
   
5. ALSA: AML-AUGESOUND, HDMI
   
6. PULSE: Default, Bluetooth Audio (PULSEAUDIO)
   

P.S. - Happy New Year to you all!