The TL;DR: The game won’t launch on current steamOS, but preview build 3.7.6 fixes the launch issue.
Unfortunately the game is unable to maintain decent frame rates even with severe reductions in graphical settings.
The drastic decrease in performance compared to Doom 2016/Doom Eternal is due to the game using mandatory ray tracing for lighting.
It’s possible that we’ll see some patches or mods that improve performance, but at launch it will not be a good deck experience.
People like you defending this nonsense is exactly the issue, but you’ll never realize it.
Cool beans. I really like ray tracing compared to rasterized GI or reflections, so I’m going to happily enjoy the game, thanks.