Hello there!
Riders Republic is currently not compatible with the Steam Deck. We're aware of this and the team is already working on it.
We do not have an ETA at the moment, and we'll update you as soon as possible on this topic.
Thanks!
Steam Deck compatibility update
Source: Steam Community (opens in a new tab)
Build and release context
Recorded Steam release date:
Within one calendar day of this post (UTC). The listed date does not establish an exact launch time.