What is up with BLACK TRIANGLES?

I’m reading sighting after sighting about a solid black triangle sighting, with visually similar features going back until the 1980s. The TR3B is rumored to be “Anti-Gravity”. I’m out of the loop: since when do we have anti gravity aircraft? — *Example cases -Belgian mass sighting -White Pines Canada family sighting on Micah Hanks -Angelo Accetta @ Lemoore Naval Airstation on Ryan Sprague -Black Triangle UAP sighting discussed on Joe Rogan with David Grusch — Why are Tom, Dick, and Nancy’s seeing these things flying by on back roads, or floating above their homes?

Lastly: Have you seen one in real life?📐