Epic Games unveiled plans for a new developer framework for online services. This framework will let other game developers add cross-platform support into their games. The SDK will be free and roll out in multiple parts over 2019.
Fortnite has been one of the best examples of cross-platform gameplay. A single player can install Fortnite on a console, a PC and a phone and find their profile on all platforms. Many games support multiplayer matches between players on multiple platforms, but very few games “port” your profile from one platform to another.
Epic - SDK - Game - Engines
That’s why Epic Games wants to make that easier. The SDK will work with all game engines (not just Unreal...