The above was one of the few solutions I hadn't tried, but sadly still no joy after giving it a go. It's as if the internal soundcard doesn't exist unfortunately.
It sounds like you're having the exact same issue as me! I received my Lafite 15.6" laptop yesterday and I'm running Linux Mint (Ubuntu based) as my primary OS. I've unfortunately experienced the exact same issue - literally everything works (WiFi, bluetooth, touchpad etc.) apart from the sound...