SBUS RC control not working for ground vehicles

QGroundControl does not see any stick input from the RC radio via SBUS if I choose any of the ground vehicle air frames. It doesn’t work either with Futaba nor with FrSky receivers, but it works with either of them if I switch to e.g. a generic quadrotor airframe. So something with that airframe type does not play well with SBUS.

Firmware: px4 1.9.2
Hardware: Pixhawk 2.4.8 (tried both knock-off and original 3d robotics)

Any pointers as to what to look for?