No such thing as free energy. Humans consume resources food and water and energy to survive like both animals and plants. Free energy would be spiritual. Possibly occult. Magical. It is fundamentally not electricity. Electricity requires moving parts and these require a plethora of resources to generate power from. So it fundamentally is not free. Let's suggest a car ran on some form of electromagnetism. The car still has to be built.

What was Babel, a paradigm for the collapse of civilization. How, they like to tell tales. Who knows. What they found of supposedly Babel, wasn't that impressive. But if what you describe existed in a past civilization it was quite unlikely Nimrod's. Although isn't Nimrod also Gilgamesh? This side of the flood would have far more evidence.

The paradigm of Babel is a common story, like imagine the lost children, these are a fictitious tribe, after a planetary extinction level event talking of TV, how the fudge would they describe it. If there is more to it, it has been lost over time. Reinvented into religion and assumed by a host of narratives and in those days they had the same authors and playwrights, without of course the TV. God's to them could've been just about anything. Like formerly projected.

However there are anomalies, least of all in the word of mouth translations changing over time. Huge anomalies where there are big questions about what occurred in our past. It has been largely scrubbed and another narrative inserted. The Summerians have quite the tales, like the rest of sanskrit. These extend into the heavens and the universe and talk of a lot stuff there are no comparable descriptions of. No descriptions at all.

But this side of the flood, dubiously there would be far more evidence and far more descriptions. Who knows. Did their gods really want such an epic reset they hammered the survivors again. Summerians caused the flood. They supposedly left the planet or some shit. But you're talking about alien invasion. Specifically in keeping this present species ignorant. Ignorant of them and their construct. But then why haven't they again today? Still ignorant? Or still not a threat?

Nuclear power stations have supposedly been found dating back billions of years ago. https://www.howandwhys.com/ancient-african-civilization-built-earths-first-nuclear-reactor-2-billion-years-ago/ .Except it's probably been debunked as natural geology. Like a lot of anomalies.

Nuclear power stations leave evidence like in that press, above, and it really doesn't tend to disappear after a few thousand years.