This is sincerely apropos of nothing, aside from that by chance I have been spending a lot of time in places real and virtual where they are overrepresented relative to the general population (including cohost!). I don't know if I'm unique in the amount of exposure I have, as a heterosexual cis man, given the unusually high and varied number of mutually exclusive social groups I pass through.
But I am truly and genuinely fascinated by how many completely different kinds of nonbinary people there are. I've known and accepted for quite some time now (after an embarrassingly late start) that the gender binary is a gross oversimplification, but I am continually amazed at just how many discrete and non-subjective forms of human identity there actually are.
As an outsider, you can become closely familiar with an entire enclave of nonbinary people, befriending dozens of people who all share the same gender for which the English language has no name, amidst thousands of people who all know each other and share that identity and are numerous and consistent enough that they can build a culture around it, ecosystems of two or three or however many genders that form a consistent community which newcomers immediately recognize as people like themselves, and still barely know anything more about gender in general than when you thought there was just male and female.
You can meet two, ten, fifty enclaves like this which share very little in common with one another aside from that they all technically fall under the umbrella of nonbinary. Sometimes even they themselves don't know how many kinds there are, outside of their own communities.
How many genders are there? Two? Three? Six? Two, yes, no, and neither? The question is unanswerable, because the question itself is wrong.
You may as well ask, how many drops are there in a gallon of water?