The plasma theory is interesting.
It leads in the direction of my theory that these may not be objects. They may be living beings that are not composed of solid bodies like we are used to seeing.
Even in the normal realm of this world, most flying things are alive, not machines.
“Living beings that are not composed of matter…”
Such beings are described by multiple religious traditions.
I think Ivan Sanderson had a similar theory.
https://www.amazon.com/Uninvited-visitors-biologist-looks-UFOs/dp/B0006BRN62