To rebind to arrow keys for steering, open config.ini and change steering to:

steerLeft = 263

steerRight = 262

throttle = 265

brake = 264

Sweet!

Thanks for that suggestion, I added them here in the docs: https://github.com/nothke/shakedown-docs#rebinding-controls

I managed to get throttle and brakes correctly mapped to the triggers on my DualSense with the following adjustments to config.ini:

brakeAxis = 3
brakeAxisDeadzone = 0
brakeAxisNormalized = 1
brakeAxisInvert = 0

throttleAxis = 4
throttleAxisDeadzone = 0
throttleAxisNormalized = 1
throttleAxisInvert = 0

Essentially you just have to decrease throttleAxis and brakeAxis by 1. This might be because, by default, the right stick is also picked up on the default throttle/brake axes.