Before nintendo switch firmware 7.0.0 came out, Nintendo switch didn't have korean and chinese keyboard in OS keyboard.
So there was no way to type korean or chinese letters in any game. even minecraft.
but in firmware 7.0.0, they finally added korean and chinese keyboard.
but game developer must update the game to load those keyboard. otherwise, those keyboards will not shown on list.
Currently, Switch version is the only version that can't input korean or chinese among all bedrock edition platforms.