I confirm that it seems to work fine. But it needs thorough testing.

My environment details: https://gist.github.com/carlos-mg89/e6fd5671bcf319e94035782cee6023ca

Distro: Linux Mint 19.1 Tessa (64 bit)
GPU: Vega 56
Driver/LLVM version: Mesa 19.1.0-devel/9.0.0
Kernel version: 5.1.1-050101-lowlatency
Proton version: 4.2-3

I can confirm the game appears to work without issues. Also the videos work (even though quartz is mentioned in the logs, this game has .bik videos (Bink Video)).

Including a log of some gameplay for scrutiny:
steam-6840.log
system_info.txt