Once upon a time in the Whispering Sands desert, there was a band called the Bintim Havah, the Daughters of the Wind. Which is to say, "fatherless daughters" who had run off into the wild because they didn't like their life in the tribe. They were sort of traders, sort of bandits, and not exactly anything. There was the one who sewed her snatch closed, and the one who made a saddle out of the tanned hide of her rapist and so on. They had a number of confrontations about gender issues. If a woman arrives pregnant and it's a boy, can she keep it? If so, when does the baby man have to leave the all-female band? Can a man be raped, or only a woman? If someone with a penis announces herself as a woman, is she or is she not? Other deserts dicker over race or religion, this one dickers over gender. Whatever.
One day, some of the Daughters of the Wind agreed with each other, and disagreed with the others, enough to peel off and become a tribe. The Taja, I think they became. And the first thing they did was sit down and throw out EVERYTHING about gender. They took it apart like a wagon in a bad neighborhood. Then they played with the loose parts awhile and agreed on two NEW genders: nurturer and provider. The former contained a lot of things commonly considered feminine, the latter contained a bunch of things commonly considered masculine ... but they were both voluntary and performative. Nobody looked at anyone's crotch and declared their gender on account of it. (Though there was that time they watched a bandit man's actions and decided that since he was acting like a nurturer, he must be one, which confused the hell out of all the bandits. They were right though.) So they went south and settled there.
Couple centuries later, another group hived off and went north, to the Brindled Hills, where they became Waterjewel. They did the same damn thing, only after they were done dismantling everything, they reassembled all the bits into five genders: hrish (masculine), hrin (feminine), hirshn (both), nrish (neuter), and shrin (I'm-not-telling). And none of that was any guarantee what was under the robes: it was statistically likely to match the description, but didn't have to, and could be anything. Waterjewel is a very weird and wonderful tribe, and most everyone else is scared of them.
There's also a bandit tribe that has what they call "the mellifluous gender," with people who can present as masculine or feminine on any given day: but always one or the other, and always day by day, neither switching in the middle nor mixing elements.
For a while, I thought those 8 options pretty much spanned the spectrum of what gender could do. That was back in junior high or early high school though. Since then, I've explored a lot more sex/gender configurations.