I watched a presentation a long time ago that went through the math of Von Neumann probes. I don’t remember the details, but it was something like a sufficiently advanced and motivated civilization could convert a Mercury like planet into enough Von Neumann probes to put one in every star system in the universe in some finite number of millions of years. The argument was something like at this point, there should be one in our solar system. And if there isn’t, why not?

I think Avi Loeb has cried alien too often and too easily to be taken seriously at this point. I think there is about zero chance any of the UAP things are anything. But I wouldn’t be too surprised if there is an ancient probe just dormant somewhere in the solar system. Would we recognize it if we saw it? Maybe not unless we got close to it. Could we find candidate objects that look out of place? Fascinating line of thinking.