By default, at least on both Nobara 41 and Fedora 42, only the Dead Center menu background appears unless you put "-background $(shuf -i 1-5 -n 1)" in the launch options. Also on Fedora 42, there's no main menu music unless you copy Portal 2's libmiles.so from Portal 2/bin to Left 4 Dead 2/bin and replace the file. Make sure the file is written in lowercase in order for the fix to work.

I don't know if it's a placebo, but PULSE_LATENCY_MSEC=60 seems to reduce audio latency. "-vulkan" replaces ToGL with DXVK and makes the game run better, and "-novid" skips the startup intro.

Had to do some work, but after all that it works rather well. I just wish Valve fixed all these issues without having to do it ourselves.