I know what LE works, and after experiences with OSMC I think it's pretty good idea.
If problem is local to me, then only thing I haven't checked is situation where system check what is connected to HDMI and configures sound device to use TV capabilities (don't know if that's even possible). Well, maybe I have to disconnect Odroid C2 from TV and reboot it. Cables, ports, TV and speakers are good, beause it worked well with Raspberry Pi and OSMC (where eg. Boblight doesn't work - on Odroid C2 and LibreELEC Boblight works fine). Problem with software (or drivers) is shown by speaker-test (only two channels detected).
Here is an output from Raspberry Pi (well, this one is not connected to any TV):
rexus@blueberry:~ $ speaker-test -c 6
speaker-test 1.2.4
Playback device is default
Stream parameters are 48000Hz, S16_LE, 6 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 480 to 10922
Period size range from 480 to 10920
Using max buffer size 10920
Periods = 4
was set period_size = 2184
was set buffer_size = 10920
0 - Front Left
4 - Center
1 - Front Right
3 - Rear Right
2 - Rear Left
5 - LFE
Display More
All channels are detected (I should connect it to something to check if it really works).
Why more people don't complain? I don't know, but how many of them are using 5.1 sound configuration (stereo runs out of the box)? More, how many of them can hear the diffrence between passthrough sound and stereo streched to 5.1 by speakers (what my speakers is doing by now and it sounds... well, not bad, but it's definitely not DTS 5.1)? Maybe I'm the first one who wants clear sound on this board