I am at an event with most of the active contributors to the Inari Sámi Wikipedia (saying this to establish that consensus is there), and they asked if it's possible to make categories sort in the proper Inari Sámi alphabetical order.
Inari Sámi is already in ICU, but it is missing ordering of two characters, Ä and Á (verify here), so until that is fixed upstream, we should add a custom uppercase collation instead.