The category collation (sorting order) for the Northern Sami Wikipedia is incorrect, as best exemplified with the category for letters of the Sami alphabet (compare to the alphabetical order). According to https://www.mediawiki.org/wiki/Manual:$wgCategoryCollation support for Northern Sami exists, but is not deployed.
I have asked for community input here, and will upload a patch for this shortly, so that when a week has passed it can be added (unless, of course, there are objections from the community, but I can't imagine why there would be).