Nintendo’s portable systems (going back to the Game Boy and including the Switch) have never had region locks, on the logic that somebody might want to buy a new game while traveling. The consoles (except for Switch) do, though.
3DS was region locked - I had to import a Japanese 3DS to play the Japanese version of Persona Q2 (or I could have used CFW, but I didn't want to risk the downloaded content I have).
Funny enough, that's when I wanted to buy a Nintendo portable. 3D without glasses seemed interesting. Then I noticed that not many games are available in eastern europe and I wasn't willing to jump through hoops to give them my money.
