Here is a nice video with good information. 12 minutes long.
Link not working...
Here is a cache of the page only from Yandex:
Yandex Cache Link
The description said the following:
Are E.Ts Living Beneath The Surface?... Mysterious Goings On Below Our Feet
1,333 views•Dec 18 2020 g.
There are many references to secret underground bases deep below the Earth's surface. Mostly they are associated with military facilities, but on occasion there are rumours of an extraterrestrial presence below our very feet. Our planet has a mass of underground caves, caverns and tunnels. Could there be extraterrestrial beings occupying these areas? Some researchers believe that E.Ts have been here for a very long time and have been interacting with mankind for thousands upon thousands of years, from alien abductions, to steering humanity.
They do appear to have another similar videos perhaps that are similar on their video page:
Notice from 23 hours ago "Are They Deep Beneath Our Feet?... The Infiltration of Humanity By The Reptilian Race". In this he talks about Robert Morning Sky (@Ephraimite you may be interested in this).
Especially, though, think on this (especially post #2):
@Soretna , I think a conclusive link will someday - in the not so distant future , be proven between the UFO phenomenon and the Hollow Earth civilisation .
Sure, they all have UFOs, demons and demigods.