According to a recent livestream, which can be found below, Fortnite for the Nintendo Switch does not require the Nintendo smartphone app for voice chat. Instead, users can simply plug in a usb microphone into the Nintendo Switch and chat away.
Fortnite is now available for free on the Nintendo Switch.
So apparently you do not need to use your smartphone to use voice chat in Fortnite on Switch, just put your headphones into the Switch and you are good to go pic.twitter.com/Mp8qNmxBjO
— Nibel (@Nibellion) June 12, 2018