Big tip for anyone that's currently trying to get this game to launch on a Linux desktop: if you're using the Flatpak version of Steam and having trouble, try migrating to the distro-specific package that Steam offers.

I was having the hardest time trying to figure out why this game would start the launcher, trying everything from SteamDeck=1 %command% to swapping out different Proton versions to reading tons of logs and searching obscure error messages. The one thing that completely fixed this, without a doubt, was moving to the .deb package of Steam from the Flatpak one.

The game now works for me without any apparent flaws...although, I'll amend my report as I continue playing. First time in a long time that I've seen something like this.