The question of ETI's or ETC's has been much on my mind for most of the past half-century. Read a great many books and articles on the topic.
For a time I was very interested in UFO sightings as well, in part because of a couple of my own (literally unidentified objects... don't know what they were, other than "behaving oddly").
The Drake Equation was never intended as a definitive answer to the question, but a framework within which to discuss and consider possibilities. We NOW can plug more accurate values into most of the variables than was possible when it was constructed, but we still have zero data on some of the most important ones.
The Fermi Paradox strongly implies we are probably alone in our own galaxy (as regards techno-civ ETCs) or else that interstellar communication or travel is simply too hard or the timelines to long. However a good book I read on FP last year suggests that part of the problem with it is "we are looking for ourselves"... for an ETI that is technological, curious, communicative and/or expansionist, another "us" or an "us squared" advanced version, when such ETI's as may be out there may be very different from what we expect.
Major factors in whether we are or may have been visited include whether C is the universal speed limit or if there is a way around it. We already know of at least two hypothetical ways around it though neither could be practically implemented with our current knowledge and tech. We don't know how far away we might be from discovering an "FTL bypass"... the answer could be ten years, a hundred, a million, or never. We can't make assumptions that ETCs with "warp drive" would necessarily be millions of years in advance of us, or maybe just decades or centuries. We don't know.
As far as UFO encounters as presented by various sources... a little digging tends to cast grave doubts on the credibility of most claiming close encounters, abductions, or similar actual-contact scenarios. I am skeptical.
Another question is if they're so advanced, why do they (the hypothetical alien "they") let us see them or catch them on radar? Of course their culture, motives and modus may be incomprehensibly "alien" as far as we know. And all the crashed-UFO stories... how embarrassing to travel light-years merely to crash in the target planet's atmosphere or get shot down by primitives!
Again... skeptical.
But on the other hand there are some cases not so easily explained away, as in the recent military footage, so who can say.
