So I've been trying to play the game using a dualshock 5 controller, but it seems that for whatever reason a lot of the buttons seem to be getting mapped to the left trigger rather than the buttons set in the options menu.

I believe it's an issue with the controller's adaptive triggers being detected as multiple input sources rather than as a singular one, so it thinks I'm pressing multiple buttons on the controller when I pull the trigger.

Sorry you're having issues with your dualshock! We have other players who use a dualshock and I haven't heard that issue, but maybe theirs don't have the adaptive triggers. I would try resetting the keybinds, and if you have any other controllers or wheels plugged in at the same time disconnect them.