UFOs are an interesting topic, just because of the wide variance in what different people think they mean.
To some, anything you can't explain is intelligent beings visiting us from other planets.
To others, everything is explained by covert military experimentation.
And in the middle? A vast chasm of other considerations, including the military reverse engineering intelligent ET tech.
That gigantic range of theories is GREAT for entertainment, but I wish there were more serious research being done and reported (not fringe stuff, more like the NYT info dump).
Personally, once you weed out the UFOs that are explained, there's about 5% that nobody can figure out.... of those, I suspect the majority are still advanced military stuff or one-off meteorological stuff. If there's anything really cool or weird happening, I'm torn between two things: (1) at some point in the future, we invent time travel, and we have seen vestiges of that, or more likely (2) we have been visited by unmanned (unpersoned? unbeinged?) probes, because THAT is how WE are exploring other worlds, not sending our actually people. I very seriously doubt that we have met and captured intelligent alien beings, but would grant a slim chance that we've been visited by their tech.