In the pass, it is possible to create a bicycle animation with Reach Target . But it might comes along with many manual keyframing work. The approach is using Reach Target, check the Reach Mode – Rotation in this manual page:
https://manual.reallusion.com/iClone-8/Content/ENU/8.0/50-Animation/Reach_Target/Character_Contacting_with_Targets.htm

In the example on this page, the character is turning a water valve with his hand. You can imagine the hand as the character’s foot, and the water valve as the bicycle pedal. In this way, you can create an animation of the character pedaling a bicycle.

However, you still need to consider the chain mechanism animation after the pedals are driven. It’s not certain whether your Sketchfab custom prop has the components separated, or whether it supports forward movement, as well as turning left or right as part of the overall motion.

So it is recommended to use the advance animation system – Motion Director to finish the bicycle animation by a few clicks setting, and control the character with bicycle just like playing game. 😉
Motion Director (MD) Ride Bike:
https://www.reallusion.com/ContentStore/iClone/motion-director/md-personal-mobility/default.html#product

Or some pre-made motions for bike:
https://www.reallusion.com/contentstore/iclone/3d-animation/bmx/default.html
https://www.reallusion.com/contentstore/pack/iclone/3d-model/hw-city-e-bikes-collection