Maybe a dumb question: Is it more probable that the UAP are extraterrestrials OR is it more probable they are an ancient civilization with advanced technology

Maybe a dumb question: Is it more probable that the UAP are extraterrestrials OR is it more probable they are an ancient civilization with advanced technology like Atlantis or Wakanda. The latter doesn't have to find earth or violate the known laws of physics. I think its a camera flare fwiw; but as I read through the comments it was an interesting thought that occurred...