PS4 and Switch Fortnite accounts lock each other out, players

Using a Fortnite account that has been used on the PlayStation 4 will keep you from using that account on the Switch, and an account that has been used on the Switch can’t be played on the PlayStation 4.

Sony Screws Over Fortnite Players by Locking Accounts on Other

In response to Fortnite accounts locked out of Switch, Sony says

Bluetooth Mobile Gamepad Wireless Game Controller for PS4/Switch

Fortnite players can finally merge accounts, but it's complicated

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Fortnite - Account merging now possible! : r/NintendoSwitch

How to Add Nintendo Switch Friends on PS4

Fortnite players can finally merge accounts, but it's complicated

How to link multiple existing Fortnite console accounts - Dexerto