So I just went back to 1 of the large landables that I myself found wayyyy back in the day. Far enough back that while it had EDSM data, it didn't have all of the data that EDSM can grab after all the latest patches to Elite.
So I go back to grab the rest of the data, FSS the system and realize that there's 2 other bodies I never scanned. I scan them and 1 is a Water World, and the other is....ANOTHER LARGE LANDABLE!
Granted, this is the smallest large landable on the list at only 118,216.93KM, I figured I'd put it on here anyways since it's in the same system as a 20,000KM one. So if you've got a planet at least 18,000KM in radius, it'll definitely be accepted.