BeamNG.drive is your ultimate vehicle sandbox:
https://www.beamng.com/
That said, it doesn't do multiplayer so if that's your thing, it's a hard pass. Also, it's a sandbox, so make sure you approach it like so. It comes with a good few scenarios and series of scenarios to give you stuff to do and ideas of what's doable (from driving tutorials to basic races and spectacular crash challenges in between a Speed reenactment), but you won't find long campaigns or unlock-based modes.
Check out that customisation video for a taster, and that was in 2016, the game keeps improving:
Edit: and here's one for jumps and crashes:
Or how about jumping into truck trailers?