Maybe this is just an ad campaign for the next season of Skinwalker Ranch.
You might be joking, but after reading considerable comments on these things, I'm leaning towards the idea that they're very sophisticated holograms. As the article above says, they tend to be seen as "floating" when they're not making some kind of direct motion, and they don't seem to actually DO anything besides look ominous in the sky. It seems more like a presentation, than an invasion.
It's the sort of thing producers of a movie about "killer drones" would do to gin up publicity, using Elon-level technology.