Nakama - Nakama is an open-source distributed social and realtime server for games and apps.
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
GameSparks - GameSparks is a Backend-as-a-Service solution provider to mobile game developers to help them...
Supabase - An open source Firebase alternative
RemoteStorage - An open protocol for per-user storage OWN YOUR DATA
GUN - Self-hosted Firebase.