Unity Gaming Services is an end-to-end platform that is designed to help you build, engage, and grow your game. Unity Gaming Services supports your entire development lifecycle. Use them to build your foundation, engage your players, and grow your game.
Epic Online Services (EOS) are free, cross-platform services for multiplayer games, includes operation tools and allows scaling. Epic Online Services powers cross-platform social game experiences with engine agnostic, open, modular, free online services that connect friends on any platform and any store.
https://dev.epicgames.com/community/learning/tutorials/05Ky/epic-games-store-epic-for-indies-tip-14-unity-unreal-switching-unity-gaming-services-epic-online-services