The sound effects work fine, but there's no music audio whatsoever(and it's turned on in the options).

Same problem here, on a Debian GNU/Linux: the sound effects play correctly, but not the music. No matter the settings.

I tried both the native Linux build of the game and the Windows build through WINE, on two different computers.

EDIT: I contacted GOG support about it, and will contact the game publisher and developer tomorrow.

EDIT 2: I contacted the game publisher, I’m going to give it a little time before I try reaching the game developer too.

I got some feedback on the Lutris forum, from someone else getting the same bug: https://forums.lutris.net/t/does-lutris-have-support-for-offline-gog-installers-and-lack-of-music-in-werewolf-the-apocalypse-purgatory/22132/6

Now I’m wondering if something might be wrong with the GOG build of the game. Does anyone actually get working music in Werewolf: The Apocalypse - Purgatory when playing the GOG build? No matter if this is on Windows or on Linux.