Looks like another title that uses Dosbox.
From the log it looks like you're missing some SDL libraries, presumably 32-bit ones? Maybe Dosbox falls back to a slower output method?
@whizse you are right, there is something missing on my Arch
tested on Ubuntu 16.04 based distro, and changing this to a whitelist request
Play button in the Steam client is sufficient.Found in the 2018-10-05 white list update.
PROTON_NO_ESYNCx1 2018-09
Compatibility ReportSystem Information
I confirm:
Log is 96MB, so google drive link:Symptoms
FPS is unstable, can drop to 6 or 11 FPSPROTON_NO_ESYNC doesn`t helpReproduction
Install and run HeXen: Beyond Heretic, play through first level at least until opening the green door