Good news !
The 3.1.0.12 version works fine for me, I have no longer sound issue, and camera is working.
I misread the instruction of post #490, copy/paste links from post #464
and just change the version, I didn't pay attention that it was sailfishos_3.1.0.12_latest/ and not sailfishos_3.1.0.12_latest_armv7hl/
So, can't work, obviously.
My bad ...

Enjoy your 3.1.0.12 !