Like, I get that most of the headlines about this stuff get clicks by talking about "zomg aliens", but everything I've read on this topic that ever seemed even slightly credible has tended to lean more towards these UAP's being totally terrestrial phenomena, just utilising one specific technological capability that we are not aware humans have developed (the ability to somehow manipulate the relativistic mass of an object within a given space).
IMO that's a much more likely scenario than reverse engineered aliens.