The biggest mindfuck about utrum/neutrum is that it exists in Danish and Norwegian as well, but the categorization is not 100% the same, some nouns are utrum in one language and neutrum in the other. So there's different arbitrary rules, and if you go from one of the Scandinavian languages to the other, you just have to learn the ones that aren't the same.

For example, "a friendship" is "et venskab" in Danish, but "en vänskap" in Swedish.