All the stated potential reason in the initial post are fascinating. Now we are seeing UFOs (Or UAPs - unidentified aerial phenomenon) being aknowledged by official governments. Most of them can be identified as something known, but a few are still a mystery.
I like an article from NPR that's says in 2021, there are 143 reported UFOs that cannot be explained. These are just sightings between 2004 and 2021.
I'm neither a believer nor a denyer, but it's clear some things can be called 'weird'.
When it comes to meeting aliens face to face, science makes it hard to believe they will just show up and say hello. But maybe they are watching.