But I can't find it. There's some third party sites like softpedia with demo's of the windows version. but I'm on linux and would love to make sure it runs ok, picks up my controller that kinda thing. Looks like a really awesome sim =)

Yea there's a demo right on this very page.

https://fpv-freerider.itch.io/fpv-freerider

Look towards the end of the page, there's a red button where it says "Download Freerider Linux demo"

There's a Linux demo for Recharged too:

https://fpv-freerider.itch.io/fpv-freerider-rechar...

Hope it will run well on your setup!