Loki turned into a mare to get properly fucked by a stallion, get pregnant and deliver an 8 legged super horse (Sleipnir) that Odin proudly rode around... yeah, they are very fine with gender fluidity
I mean, Loki was ultimately a villain, so it's more like they perfected the queer-coded villain archetype, but there's also evidence both that Shieldmaidens were a thing and some Shieldbrethen were assigned-as-Shieldmaidens-at-birth. How accepted that would have really been we simply do not know, or how much norms changed by region and time. Or even whether they would have thought you were stupid for asking if ladies could fight in "men's clothing," aka, armor.
There is also quite a lot of difference between a Dane, a Kievan Rus, and a citizen of what was basically a republic in Iceland in 930 AD.
Pretending the Vikings/Norse/Whatever were some pinnacle of ancient tolerance is just as wrong as pretending they followed practices that map 1-to-1 on modern bigotry. They were an immensely patriarchal culture, whose economy was quite literally based on chattel slavery on a scale that would only be matched by American plantatioms, with a whole slew of what can only be called toxic masculinity, who only could ever look good in comparison to Roman and Abrahamic norms, but that's the comparison Westerners will inevitably make in their favor because that is the standard they know.
Doesn't Loki being a villain vary from myth to myth? In some he's just mischievous, in others outright malicious.
The Ragnarok myth has him leading the armies of the dead, but I've always wondered how modified the story is due to the influence of Christian monks...
Pretending the Vikings/Norse/Whatever were some pinnacle of ancient tolerance is just as wrong as pretending they followed practices that map 1-to-1 on modern bigotry...
I'm not pretending any of that... nor I am implying they are an example of morality about anything... All I am saying is that, what we now call "gender fluidity" or simply anything in the "LGBTQ+" spectrum does not seem to be, in and of itself, a "sin" or a morally reprehensible act in the Nordic mythology.
Also, Loki wasn't really a villain... he was more the "anti hero" type... From all the Nordic mythology I have read (I just like it, I'm not a scholar) the attitude towards him always seemed to be "Damn it Loki, we could get along if you stop being an asshole for a day"... not "I shall vanquish Loki and end his evil ways"