https://www.gamespot.com/articles/fortnite-mobile-update-adds-a-much-needed-feature/1100-6459306/

You no longer have to suffer (or win) in silence, as Fortnite has added voice chat on mobile devices. The new option is available in the Settings menu, which will let you push-to-talk with party members. Fortnite is available on iOS devices, with an Android version forthcoming.

The feature was announced in the v4.3 patch notes, which also added shopping carts and mushrooms and two limited-time game modes. The voice chat is the most significant new mobile-specific feature, though, as the ability to talk with teammates has been lacking on the platform. Fortnite's next set of challenges have also been delayed to Thursday, which will serve as the new drop date.