I had to give up on getting Assetto Corsa to work on Linux for now - I know others got it to go but I've struggled quite a bit and I saw that rFactor 2 is certainly easier to get working (maybe what I have learnt may apply to AC I'll have to see).
So here are a few tips for others, so they don't get stuck like I did (thanks to the guys on the Discord channel that gave me some help):
* In Steam menu Settings/Steam Play I set mine to enable Steam Play for supported titles and under Advanced run other titles with Proton-5.4-GE-3. The GE version is a bit better than standard Proton that Steam provides. The Proton GE files just get dropped into a folder under Steam and after a restart you will see it available. Proton is essentially providing all the Wine driver support.
* I installed rF2 originally under Win10 to my shared NTFS partition. Fact is this could create problems with paths from the Linux side (and some default settings), so in the end I removed rF2 completely and re-installed from Linux side in default Steam library folder (on my Linux drive) with Proton GE set, which should ensure all the right Proton files are installed.
* Standard rF2 would just fail on start after a few seconds, so right clicking on the rF2 app select Properties and then Beta tab and choose Public Beta version. On the General tab ensure there is a tick by Force the use of a specific compatibility tool, and it should show the Proton GE option. Also click on SET LAUNCH OPTIONS and enter '-force32' without apostrophes to force 32-bit mode. Then you need to restart Steam otherwise it still fails.
* I also had an issue with the app sometimes freezing while loading a track at around 95%. I noticed a 'gMotor 2 error' window that reported issues loading weather layers. If you get this try switching to a different track for one thing, and leave video settings on auto as far as possible.
* I also had issues with my Speedlink Drift Oz steering wheel (yes it's a cheapy with no driver support) - I had detected the correct functions for steering and throttle / braking but my car kept taking off at high speed in the pits and just crashing. The calibration in rF2 was showing everything was 100%. I did two things in the end that fixed it (not sure which one!): Opened Game Controller calibrator in Linux and just ran the calibration for the controller (steering wheel), and I also disabled the Auto Pitlane (press F10 in game).
After that all was fine except no force feedback works on my steering wheel. On my shopping list now is a Logitech G29 which is probably the widest supported steering wheel in racing games, and therefore also has lots of community advice and assistance. Now starts my long uphill slog to get to know all the details of this advanced racing sim.
A last tip is if you have graphics issues you can also try deleting the Config_DX11.ini file in /steamapps/common/rFactor 2/UserData/ and it will be freshly recreated.