I haven't found a fix yet, but the problem seems to be caused by the new audio system used in some newer distributions (pipewire instead of pulse audio). I had no problems with the sound in Ubuntu 20.04, but after an upgrade to Ubuntu 24.04 the sound was gone.
The game just uses a wrong output device. In another thread someone complained, that the game always uses the laptop speakers, instead of the headphones. so that seems to be the same issue.
When you run the command "wpctl status" in a terminal, it will list you any applications playing sounds and which output device they are using. The game is listed as "FMOD Ex App". On my system its using a wrong device - but I haven't found a way yet to change it. The game does not seem to use the default device set in the OS.
[edit]I now at least found a workaround: While the game is running, open the sound settings of your OS, change the default sound device, then change it back to the one you want to use. The game now uses the correct sound device. Sadly it won't remember this on the next start, so you'll have to do this everytime...[/edit]
Post edited 13 hours ago by macbest.718