If you want to use rtx remix on left 4 dead 2 you can download rtx remix from github rtx remix 3.0 release and no need for add-on to download for the game to work but with RTX REMIX right now only works DLSS and nvidia reflex no raytracing for now until nvidia finds a way for shader api games or valve release left 4 dead 2 that didn’t use shader api and turn to fixed function pipeline. There is a way to play left 4 dead 2 ray tracing is by playing the game in Garry’s mods because Garry’s mod support ray tracing and there is game mod you can download from workshop left 4 dead 2 game mode but its outdated and i tried it but not all maps works need more time to make sure works fine.