I've had a look at this article but it's unfortunately rather vague. The most concrete claims I could find seem to be about The Heavener Runestone and similar stones. Are they evidence of the Norse in America in pre-Columbian times? Or are they more modern? Are they even genuine? No one seems to be sure yet.

These sites mentioned in the article -- without knowing more than that they are "in the hills," it's more or less impossible to find any information about them.

The rest of the article is full of assertions which may or may not be true. I'm afraid I'm not all that eager to buy into unsubstantiated conspiracy theories.