I marked all the answers "YES" but it comes with a caveat: Running just with Proton, the game never found my NVIDIA GPU and instead used the integrated one, resulting in 30-50 FPS.

• To fix this, I installed GameMode by feralinteractive, an app you can install from their GitHub page (or from apt-get, depending on your setup). It's a bit tricky to get working (you have to get the gamemoded.service daemon functional first).

• After I got GameMode functional, Dredgers immediately ran off the NVIDIA GPU like it was native. Note: I used NO launch parameters.

Summary: The real verdict here is that GameMode is a pretty awesome tool for fixing an otherwise unplayable game.