Question for you: have you had many transcendent experiences in your life? Maybe psychedelic ones, but not exclusively so? Have you ever had your understanding of reality so completely questioned that you have to step back and rethink everything? Have you studied (to avoid the woo woo stuff for a second) the holographic universe ideas, multi-worlds hypothesis, simulation theory, or quantum weirdness such as the quantum entangled delayed double split experiment which essentially proves what we do in the now can actually change the past?
To use the example you outlined:
"the lizard people living in the Earth's core created coronavirus in order to usher in the return of Elvis"
If our understanding of reality is completely off, this may not be as crazy as it initially seems. Let's say "the earth's core" isn't really a thing because the "earth" as we understand it is actually 2D, and we are seeing a 3D projected holographic reality. So there could be, from the view of higher dimensional beings, a way to come out of the "core" on the 2D and project into higher planes such as 3D and beyond. The "lizard people" narrative is another interesting one. Why do people groups all throughout history have similar stories and histories regarding these types of beings? Why are demons and the like so common in our folklore? Why do many different spiritual traditions all have similar ways of describing the same thing from their own brand? As to Elvis... many do include reincarnation as their reality and even beyond that, the concept of an absolute unbounded oneness where our individuated units of consciousness are just projected illusions of the ONE.
Before you write me off completely as having lost my mind ("Luke, I could barely handle the bitcoin/anarchy stuff, but this???!?! Geez man, come back to PHP."), please truthfully and sincerely consider this thought experiment:
You've never known anything but visible light. Someone tries to convince you of mythical sounding frequencies outside of what you can perceive with your eyes which allow for all kinds of magical things like X-Rays, WiFi, Radio, etc, etc. You've never experienced those things, so you doubt it all. Let's say you then experience one of those things. You don't have a framework or scientific tool to understand, so it seems like magic. Later, you gain experiential knowledge, understanding, and tools. Now it all makes sense scientifically according to your epistemology.
Are you open to the possibility that your perception of reality is somewhat similar to this? That you don't yet have experiential knowledge about the fabric of existence than many others do and scientific tools are just starting to catch up with?
Luke, I can barely handle the bitcoin/anarchy stuff. :-P
The solution to your question is what I already stated: The scientific method. Science regularly said "well, that was wrong, gotta rethink this." That's what makes it so reliable, and made it able to usher in the greatest advancements in human knowledge since ever. Making a change is not always easy; it requires evidence, data, and a good logical argument. But in time, those win out.
But if someone still thinks the moon landing was faked? Or that the global climate isn't getting warmer? Or that vaccines cause autism? That's just deliberate ignorance of the facts, and no, you don't get "alternative facts."
When considering alternate opinions or perspectives, which you can and should do, you should always evaluate them rationally. If they fail a rationality test, then... no, I am not going to stay open to them.
I have never seen X-rays myself, but I have seen ample evidence that they exist, and have trust that the institutions and people that study them are, overall, honest about their findings. (The best way to evaluate someone's honesty: What happens when they're actually wrong. Do they own up to it or try to cover it up? If they own up to it, I am more willing to accept their word for it the rest of the time.) If the current understanding of electromagnetism was way off, we would physically not be able to have this conversation. Are there gaps and details that we don't understand or may have wrong? Absolutely, and science freely acknowledges that. But "there is no such thing as ultra-violet light" is... no, not actually a thing.
An alternate epistemology has to justify itself rationally. If it can't, then no, I am not going to accept it.