Here's a few fun ways to explore queerness with non-human cultures for your fantasy and scifi worlds!
- give them more cultural genders. Not just "nonbinary as a third gender", give them some weird genders! Sub-genders, even! And don't make it all tied to their biology, though having a variety of biological sexes is also a lot of fun.
- maybe they don't have genders the way we usually define them, and they use something else as an important identity with associated pronouns and outward expression.
- get creative with their relationship structures. Maybe polyamory is their normal. Maybe they have a committed partner most of the time, but then they have a breeding season where anything goes. Maybe they are functionally an aromantic culture and they don't really do committed relationships like that.
- if they have distinct biological sexes, what options are available for those who want a medical transition? Maybe it's a more low fantasy world in a historical setting and they don't have that option, but what other steps might they take to "pass"? If their concept of gender or an equivalent identity has nothing to do with their biology, what does it even mean for them to be trans?
- in a species where biological sex is naturally flexible, shifting between egg and sperm production on a whim or just because of environmental changes, what does that do for their gender culture?
- interspecies relationships are inherently a little queer, when you think about it. What does attraction between species look like? Are there some cultural barriers they have to navigate?
- if queerphobia exists in your world, don't be shy about exploring the effects it actually has on the characters. If there is no queerphobia, what does that really look like? Was it a struggle to make that happen? Think about the generational history a little, and how different it might look to our own reality.
and please, just like with disability, religion, fatness, and varied ethnicities, if you find yourself coming up with excuses for why queerness of any sort could not possibly exist in your world, even if you think "well just not for this specific population" maybe examine that a little deeper and ask yourself why.