In my opinion, the target of the Ansarallah ballistic missile attack on Riyadh was likely King Salman Airbase, just south of Riyadh.

If the target was Prince Sultan Airbase, there likely wouldn't have been any early warning alerts for Riyadh, as it is located 80 km from the city. Early warning alerts typically weren't triggered for Riyadh when Prince Sultan Airbase was attacked by Iran earlier this year.