DnD forums were the first place I even heard of the term "non-binary" heard it there probably a half decade earlier than anywhere else. I knew of the concept of several genders from anthropology, but it was always frame as a culture having a specified set(not being able to make up your own, and ours had two that were biologically based on sex), and it was always on the person wanting to be a supernumery gender to convince the rest of the community they were that. "Misgendering" was not a thing.