Currently in Early Access, Wheelz2 is a 3D moto-trials game inspired by some of the 2D classics like xmoto.
Originally released on Steam back in May of last year, Linux support arrived only a few days ago. Powered by the Unreal Engine, Wheelz2 actually does look surprisingly good and quite a bit silly on some of the tracks.
The official trailer is quite old, but it should give you a reasonable idea of what to expect:
What makes this one interesting, is that the developer is working on both local and online multiplayer, which certainly could be a big barrel of laughs. Both of which are already partially in according to the Steam page but quite rough with the developer noting both features are "alpha quality".
Eventually it should get a level editor and modding support.
You can find it on Steam.
Hat tip to Werner.