no issue in launching, just use latest proton ver

you can use wallpaper engine to download wallpapers only, you can't change them through it. from what i gathered, it works on KDE plasma only (might be wrong) and you have to download a plugin.

right click on desktop to show cursor menu, go to desktop and wallpaper. in the wallpaper tab you can get new plugins there, find a plugin called wallpaper engine for kde. download it, then select the wallpaper type to the plugin just installed then click on library just under wallpaper type.

find the path to your SteamLibrary. dont select anything from inside like wallpaper engine itself, just SteamLibrary and the plugin will know where to go from there.

if it still doesn't work i found a few good youtube videos that explain the process. they will provide more details. as i have downloaded somethings that im not sure are they needed to run wallpaper or not so im not going to mention them here.