Fortnite crossplay (Nintendo Switch, Xbox One, PC, Mac, Mobile) confirmed, Sony blocking PS4

Sony enabling Fortnite cross-play for PS4 against Xbox and Switch - The Verge

Fortnite Switch Can Play Online With Xbox One, PC, Mac, And Mobile - Game Informer

Fortnite: How to Play Split-Screen

How to Enable Crossplay in Fortnite (PS4, Xbox One, Switch, & PC)

Can PS4 and Xbox play Fortnite? - Quora

Fortnite Cross-Platform Play Accidentally Activates Again

Load into the Lobby in Fortnite - Game Mode Select Screen Removed

PS4 & Xbox One cross-play briefly enabled for Fortnite

Xbox's Phil Spencer comments on cross-play support after Sony blocks PS4 Fortnite accounts from logging in on Nintendo Switch - MSPoweruser

PS4 Xbox One Cross Play Working With Fortnite, But Corrected by Epic Games