I don’t assume anything (nice strawman) other than that there are coherent explanations that would explain the presence of non-human technology in our atmospher

I don’t assume anything (nice strawman) other than that there are coherent explanations that would explain the presence of non-human technology in our atmosphere that do not require things like FTL travel. If we are going to weigh “extraordinary” phenomena then things which would require breaking known laws of physics far outclass those which do not, and many people jump to the conclusion that for non-human tech to be here it would have to have violated known physics. (It sounds like you are in this group.)