Its NA. What problem exactly you had on Switch?
Its was not exactly a problem but i just didn't want to go online with my modded system, Switch is more easily to get banned than a 3DS if you install games illegitimately as .nsp (equivalent to installing a .cia game on the 3DS).
So i just used a save from someone else who had the DLC already downloaded and restored on my own Switch, it just worked. Since the 3DS MH games DLCs works the same way it's possible it will work as well.