Unfortunately, I need to join this club. I only just got this phone, admittedly cheaply on eBay as it was sold for spares. I'm now feeling stupid because while the auction did mention problems I haven't encountered myself, I didn't notice until just now that it mentioned a lack of sound. D'oh. Anyway...
I know it definitely made a sound at one point because I initially installed the "Spookified" ArrowOS and when I went to see what the ring tone sounded like, the weird laughing sound creeped my wife out. :laugh: That's the only time I recall it ever making any sound. I don't remember ever hearing the "Hello Moto" sound on boot. Bluetooth audio, on the other hand, works fine but that obviously works in a completely different way.
What I have noticed is that /proc/asound/cards almost always contains --- no soundcards --- and dmesg shows a similar message from ALSA on boot, along with errors saying that the driver should defer loading. That obviously wouldn't help matters. What's interesting is that sometimes, and this is entirely random as far as I can tell, the card is there but it still doesn't work, with audio-related errors in logcat. I guess if it only works sporadically, it at least needs to be working at boot time if it's going to work at all later.
I initially chalked this up to teething problems in ArrowOS but no one else had reported anything quite like it and the subsequent update didn't fix it. Neither did the LoonyKernel and I noticed that /proc/asound/cards is even empty under TWRP. I realised I didn't have the latest firmware so I flashed the stock Nougat ROM that's posted here, tripped over the IMEI=0 issue along the way, fixed that, but still no damn audio.
I'm starting to think it must be a hardware issue but a loose speaker cable seems unlikely. I wouldn't expect the kernel to notice that and certainly not for it to cause the sound card to fail to initialise. I'd really appreciate it if any of you still suffering from this could check /proc/asound/cards. You don't need to be root.