Full Crossplay Support Comes to PS4 Starting With 'Fortnite

The open beta allows crossplay, progression, and commerce across the PS4, Android, iOS, Nintendo Switch, Xbox One, PC, and Mac platforms. 

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

Sony's walled garden cracks open: Cross-console play comes to PS4

Why cross-play matters - Epic Online Services

Sony offers hope on PS4 console cross-play

Fortnite: Save the World - Wikipedia

Fortnite is coming to iOS, will sport cross play with PC and PS4

Gearbox Is Adding Borderlands 3 Crossplay, But Gearbox Was Told To Remove PS5 And PS4 Support - Game Informer

Sony finally opens cross-play for Fortnite for the PS4 - GadgetMatch

Fans Forcing Sony Into 'Fortnite' PS4 Crossplay Is A Watershed Moment For Gaming