r2modman is also what I use, at this point I think I have 3 versions, Windows Exe, AppImage and pacman. I don't remember what one worked in the end but I remember one couldn't find the game even if manually located. One failed to render anything other than a black image and the last (working) one is just really slow until I get into the actual mod selection, then as before the working one can't actually start the game for some reason, it does give you the parameters you need to throw into steam to start the modded version instead. Maybe I'll poke at it again soon, I just don't want to run into issues when my friends are already ready to play the game.