I ran across the Donald (Donny) Marshall material over five years ago. I did confirm one story at the LA Times archive (since scrubbed) about the underground tunnels under Los Angeles that were discovered in the 1930s with radio waves. The tunnels had rooms filled with gold, which since have been excavated, Bunker Hill area Downtown.
Local Indians had legends of Reptile People living underground in that area.
Indigenous stories of Ant People (Greys?) living underground in the Grand Canyon also exist while the Marble Canyon stories about a portal into an underground world of "Egyptian" pyramids and gold are still researched today.
Perhaps the so-called extraterrestrials are actually "intraterrestrials"? Up is down in opposite world, y'know.