Sony's PlayStation 4 cross-play feature is out of beta and now available to all developers

The cross-play feature is now open to any game that supports it.

PlayStation 4 system software - Wikipedia

PS4 Crossplay No Longer in Beta, All Games Are Now Free to Add It

PS4 Cross-Play Exits Beta, Now a Full Feature For Developers - IGN

PlayStation 4's new beta software reduces clutter, improves multitasking

PlayStation announce cross-play and cross progression for Fortnite on PS4 with all other platforms - Dexerto

PS4 Will Support Crossplay on All Games

After six years Sony finally opens up the PS4 to cross-platform multiplayer support

Sony Starts PS4 Fortnite Cross-Play Beta - Game Informer

Sony Finally Enables Fortnite Cross Play Support On PlayStation 4: Open Beta Begins Now

PlayStation 5 - Wikipedia