I am on Arch Linux. The previous Mandible version works almost flawlessly, but Omentum Update (published on GOG on 2025-04-29) fails to run, erroring on missing "libsteam_api.so":

$ ./start.sh
Running Death Road to Canada
./prog-linux-GOG: error while loading shared libraries: libsteam_api.so: cannot open shared object file: No such file or directory

Running ldd on the main executable "prog-linux-GOG" says it has a hard dependency on "libsteam_api.so":

$ ldd prog-linux-GOG
linux-vdso.so.1 (0x000076b8d86cb000)
libSDL2-2.0.so.0 => /usr/lib/libSDL2-2.0.so.0 (0x000076b8d8617000)
libSDL2_mixer-2.0.so.0 => /usr/lib/libSDL2_mixer-2.0.so.0 (0x000076b8d85e4000)
libGL.so.1 => /usr/lib/libGL.so.1 (0x000076b8d855e000)
libGLU.so.1 => /usr/lib/libGLU.so.1 (0x000076b8d8507000)
libm.so.6 => /usr/lib/libm.so.6 (0x000076b8d840f000)
libsteam_api.so => not found
libc.so.6 => /usr/lib/libc.so.6 (0x000076b8d821d000)
libGLdispatch.so.0 => /usr/lib/libGLdispatch.so.0 (0x000076b8d8165000)
libGLX.so.0 => /usr/lib/libGLX.so.0 (0x000076b8d8133000)
libOpenGL.so.0 => /usr/lib/libOpenGL.so.0 (0x000076b8d8108000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x000076b8d7e00000)
libgcc_s.so.1 => /usr/lib/libgcc_s.so.1 (0x000076b8d80d9000)
/lib64/ld-linux-x86-64.so.2 => /usr/lib64/ld-linux-x86-64.so.2 (0x000076b8d86cd000)
libX11.so.6 => /usr/lib/libX11.so.6 (0x000076b8d7cbf000)
libxcb.so.1 => /usr/lib/libxcb.so.1 (0x000076b8d80ae000)
libXau.so.6 => /usr/lib/libXau.so.6 (0x000076b8d80a9000)
libXdmcp.so.6 => /usr/lib/libXdmcp.so.6 (0x000076b8d809f000)

The game cannot find the steam dll because the system does not have Steam installed. I guess the Steam version was accidentally uploaded to GOG.

Is this still unfixed / did you try to contact the developers?
This would be relevant for me as well.
Apparently there are also drop-in replacements / emulators for the Steam API / library, such as "goldberg_emulator" on gitlab (did not verify myself), might be worth a look.

The issue is still there.

There is also a support thread on the same issue in the Rocketcat Games Discord with very little visible progress.

Even, I noticed that the Linux version of Omentum update of the game is now gone from my GOG library, and it just has the previous Nerve version. Its called 'MANDIBLE+NERVE Update' and I don't know why MANDIBLE is in the name along with 'NERVE'. So GOG even removed the broken Linux Omentum version and downgraded to the previous Nerve version.

I can still download the Windows version of Omentum on GOG. Haven't tried it myself but running that under WINE or Proton could be the best option.