Hello @springwurm, this issue should be mentioned to the game's dev(s).

Ups, i just saw, someone opened a thread some time ago: https://steamcommunity.com/app/733760/discussions/0/1692659135907023697/

@springwurm, as noted already, this is a problem caused by the game distributor, who did no testing on Linux at all. Even if you'll manage to run the game, it will be unplayable due to ancient DOSBox version bundled with the game (e.g. due to input issues your car will seemingly "slow down" every 10s; your keyboard might also not work at all if you're running Steam via XWayland). Some of those issues will be also visible when playing via Proton - but it's not a Proton problem - these are bugs in DOSBox.

In the interest of users, who might find this issue simply looking for ways to make the game playable - you can install dosbox-staging and run the game via Boxtron compat. tool - after selecting the second option in Steam launcher menu, you should get a perfectly playable game, without any input or performance problems.