I'm running Gentoo Linux (which I know is not officially supported), and after updating Pathfinder Kingmaker to 2.0.4 the game won't start, it just showed load screen "First time load can take several minutes". I've read logs and discovered that actually one of static library, libAkSoundEngine.so was missing, so I've copied the library from 2.0.3 (or 2.0.2, cannot remeber, really) setup, and it fixed the issue. The library is located in game/Kingmaker_Data/Plugins/x86_64 directory.
Probably, would be helpful to someone.

I also run Gentoo, and have had to replace libAkSoundEngine.so with the one from Pillars of Eternity 2 since 1.x in order to get any music at all. With 2.0.4, I finally no longer have to do that. So what you're saying is that they fixed it for me while breaking it for you. Do you use pulseadio? I don't. Maybe that's the issue. One works with pulseaudio, and one doesn't.

Yes, I use Pulseaudio. However, there was no shared library binary at all in my 2.0.4 installation, not even one that doesn't work. Everything work fine in 2.0.5c though, even music is now there.

OK, maybe there was an issue with the installer you used. Mine has a working libAkSoundEngine.so, and the game works fine. It's not like they don't ever silently replace installers with working ones. You didn't actually say that the library was missing (actually, there just seem to be some missing words there), so I assumed you had issues with the new libAkSoundEngine.so. Sorry. I won't be able to test 2.0.5c for a while now. 32G downloads (No patches) without notification. Just lovely. Plus I'm on a slower line on the weekends, and have several other large games that also updated (without notification, either).

Ironically, the words "was missing" was missing in my original post =)