Undertale (Steam) won't run in DRM free mode

The Steam version of Undertale won’t run in DRM free mode on Lutris, despite the fact that it does run (with a few errors before it launches, but it does launch) through Steam itself, as well as with DRM free mode disabled.

lutris --submit-issue output: Ubuntu Pastebin

lutris -d output: Ubuntu Pastebin

Game log:

Started initial process 11822 from /home/***/.local/share/Steam/steamapps/common/Undertale/runner
Start monitoring process.
/home/***/.local/share/Steam/steamapps/common/Undertale/runner: error while loading shared libraries: libopenal.so.1: cannot open shared object file: No such file or directory
Monitored process exited.
Initial process has exited (return code: 32512)
All processes have quit
Exit with return code 32512

Weirdly enough, the file that the log says doesn’t exist belongs to a package that, as far as I could check, actually is installed on my system, so I have no idea why Lutris thinks it’s not there. Any help with this is appreciated.