there are cases where it might vary, I have a friend who get Splatoon 2 in UK and the DLC in the US and it didn't work, but another friend with the US version of Mario Kart and the Japan DLC works.The best thing to do is try to buy the DLC from within the game itself,so go and try, maybe it works :>

Sadly it wont work, Both the DLC and the game must belong to the same region. Even if the games are region-free, the DLC is linked to the game, not your account. Therefore, both must belong to the same region. Here's the Nintendo UK FAQ that confirms this
www.nintendo.com/en-gb/Suppor...

Ummmm, c-side?/jk

>:0

Don't mind me, im just gonna yoink this c:<

Q U I E N E S D A R M A!?/jk

Guys, I think she likes splatoon, Idk how, but something gives me that clue 🤔

No more bots with questionable content and no more ads, I'm starting to like this place

I am not only welcoming you, I am also giving you a strong and loving hug >:D!

Welcome sis :>