I'm a (former) student of history, so questions like that would be fascinating to me as I love history as a study of culture and society more or less. Unfortunately, I did not use my oppurtunity to learn that part of queer history. I'd love to hear how nonbinary express their gender identity within their own language. Bonus points if you have any historical examples of nonbinary people from your culture. Linguistics is not a strong suit for me, so my knowledge in that area is limited for me.
Many people in Germany use they/them or the slightly more German sounding version of dey/dem because the "th" sound is difficult to pronounce for many Germans. Others circle through binary pronouns. Some just use the binary pronoun that comes closest to what their gender is and use they/them in English only. Some use neopronouns like xe/xir or similar, whatever works best for them
Another variation I've seen in german is just using their name. So instead of "This is Alex, they are my friend, I met them at school and their favourite subject is maths", I might say "This is Alex, we've become friends after meeting at school. Alex' favourite subject is maths." (or in german "Das ist Alex, wir sind befreundet, wir kennen uns aus der Schule. Das Lieblingsfach von Alex ist Mathe.")
Italian NB-advocates tried to use the schwa letter, but it has yet to take hold quite enough, it's almost exclusively used in queer spaces. I have yet to meet people who exclusively use the schwa for themselves, most people use both or either male or female. I try to avoid using gendered language as much as possible, even referring to them as individual or person to get around it. If I can't do otherwise, I use schwa or male/female (if they use those). I have different pronouns in Italian (lui/lei, and mostly lui for safety) and English (he/they/she).
I am a binary trans woman, but I take a casual interest in nonbinary gender expression
Iceland's nonbinary community standardized on a specific neopronoun, and a term for nonbinary people, and the use of neutral declensions instead of masculine or feminine forms. These are widely used and preferred among most nonbinary people.
The neopronoun is Hán. For comparison the established gendering pronouns are Hann (He), and Hún (She).
Nonbinary people are now commonly labeled as Kvár. This term has some resemblance to the english language term queer, I suspect that's intentional. The pre-existing gender terms in casual speech are Karl (Man) and Kona (Woman).
If you miss a word in a language, you create it. Every word in every language had been made up at some point. My pronouns in Dutch are die/diens/die and hen/hun/hen. Which are also the two most common sets of genderneutral pronouns in Dutch. Die/diens/die already existed. People use it all the time if they don’t know someone’s pronouns. Similar to singular they in English. (But in both languages enbyhaters refuse to admit it and complain about how hard it is.) Hen/hun/hen is a translation of plural they/them in English. The problem is, that plural they/them in Dutch is zij/hun/hen. And zij also means she. So of course a lot of nonbinary don’t like that. That’s why we changed the zij to another hen. So literally them/their/them.
in french we mostly use the neo-pronoun "iel" (il+elle)