“there are no traces of this devastating worldwide event that would have affected all life forms”.

Nevertheless, this story can be found in many independent indigenous cultures all over the world. Can we dismiss them all?

And what about the various underwater buildings, even apparent whole cities that have been discovered by divers? It's not hard to find sources for this. Perhaps the Christian literalists have just got the date wrong, as is likely given your exposé. It was likely much earlier.