I was not able to play any file, do you?
It does not register itself as a sound source in pulseaudio

@Mic92 I am playing normally here. It's a screenshot I have taken just now:

https://imgur.com/a/2LVei

does it work for you? @groxxda

I tried using it, but it didn't output any sound. I checked Devices under File, and there were no devices detected either.

News?

@AndersonTorres well, two people did not managed to output any sound.

Hmm.. also tried this and didn't get any playback working, devices selection empty as well.

I also noticed lots of sqlite errors like this:

Error: SQL ERROR: Store setting: Cannot insert setting remote_control_port
Error: attempt to write a readonly database Unable to fetch row
Error: INSERT INTO settings VALUES(:key, :val);

Just from looking at the error that @cryptix pasted, I guess that the program tries do an update of a sqlite database that is in nix-store and thus read-only.

What remains to do on this?

I don't know. It worked fine here in my machine, but I can't know why it is failing on others.

Now the baddies: I updated the sources, but now it isn't working anymore: it doesn't find any sound cards.

Middle news, if someone is interested: I am in contact with the Sayonara team (specifically Lucio Carreras, the main programmer). I hope to return with news!

As I have no more hope working on it, I will close it without resolution of merit. Maybe another time I will consider it more closely.