Finally I have solved the audio issue. I have used the proposed solution creating a file named asound.conf in /etc with the working config via SSH.

If I reboot, the problem remains because system always deleted the asound.conf, so I use chattr bash command for make it "undeletable" for anyone, even root.

So the solution has been:

chattr +i /etc/asound.conf

Thanks to everyone who helped me and thanks to RecalBox Team!