Regretfully most racing sims (and any other sims that use peripherals) are still a huge pain to get going, even with Proton. At most you can get the actual game "running" (with performance sacrifices over Windows), but you still won't get things like Force Feedback, and half your peripherals features probably won't work (or will work intermittently for no reason).
I'd love nothing more than to never use Windows again, and I use Linux for 90% of my daily use, but if I have to have Windows still installed for any major games at all then it's just easier to keep using Windows for all gaming, where gaming really does "just work", every time.
I wonder how those force feedback wheels from different manufacturers all work on Windows, is there any kind of standardised API for that stuff? I had a brief look at sim racing peripherals on Windows and even there it seemed like each game you wanted to play had to support your specific model of wheel.
I'd love nothing more than to never use Windows again, and I use Linux for 90% of my daily use, but if I have to have Windows still installed for any major games at all then it's just easier to keep using Windows for all gaming, where gaming really does "just work", every time.