You can install it as a flatpak via the Discover store - and then use the Protontricks Launcher in the start menu to run specific applications in a game’s Proton prefix (see the README for details).

I had to do this to get Max Payne 3 working as there was some issue with the Rockstar Social Club and launcher (in Desktop Mode, I re-ran the installers Steam installs with the game files manually in the prefix, and then ran the Social Club itself to log-in manually).