I think Glasgow Airport with a runway at just 8,743 feet long is the shortest that has regular A380 service. Do you know of anything shorter?
The shortest runway with regular A380 flights
Discussion about it from a few years ago:
The runway is not the only thing in question. A 380 could run on almost every international airport in terms of runway. But not many are able to handle the two stories aircraft at the gate. All the facilities for doing it are missing.
Emirates did a runway takeoff with lots of headwind in Christchurch which only used 800m (approx. 2500 feet) of it.
Your guess about Glasgow for the shortest runway seem to be valid