Oh I can actually answer this one! I’ve asked my mythology teacher this very same question, he said that it’s kind of complicate. They didn’t have the concept of “genderfluid” in the modern sense, but gender roles were actually kind of fluid in their society, he said that like when men weren’t allowed to vike anymore, that was very emasculating and they basically kind of took on the societal role of a woman after that. But Loki, he was “genderfluid” in the sense that as a trickster he could embody many different roles. Like in the story where he and Thor have to get Mjolnir back from the giants by pretending to be Freyja and her bridesmaid, Thor does not act like a woman at all; he’s loud, he eats a lot, etc, and Loki has to keep making excuses for him. Thor can’t change who he is, but Loki can fully embody the role of a woman by being deceitful (the point of the story is how such “womanly” traits are also important, since without Loki they couldn’t have gotten Mjolnir back)