You still need vision input, so undo
EKF2_EV_CTRL 15-->13 (remove external vision sensor aiding from vertical position calc)
to ensure vision is aiding 3D position, yaw, and velocity. Then select range sensor as primary height input (EKF2_HGT_REF).
for your purpose, you only want vision + range_finder as input sources into EKF (obv. you want to keep IMU data; no baro, no GPS). So ensure EKF parameters are turned on for only vision + range.
Prior to flight, ensure the local_position supplied to PX4 from voxl qvio exists, that the position data makes sense (upon power on, should be 0s for xyzrpy on level ground), and that picking up the drone and moving around physically known distances (use a measuring tape or something) results in a corresponding update to /fmu/out/vehicle_local_position (I think that's the correct ROS2 topic) or instead of /fmu/out/vehicle_local_position, you can mavlink inspect local position
For the Starling 2, since default params were vision only, my intent would be to turn on the range sensor and then update EKF2_HGT_REF to range. So maybe reset your parameters back to default Starling 2 params and make those adjustments?