The Blueprint script posted in this thread worked for me, but shortly after saving my changes UE 5.0.2 crashed. When I restarted the editor, though, the unwanted Actors were still gone, so I’m calling it a success overall. Thanks for sharing this trick – I didn’t realize a Blueprint DestroyActor call went beyond what the editor’s context menu does.
I’ve also reported the bug to Epic about being unable to delete World Partition landscapes.