Contentful - You don't need another CMS. You need a better way to manage content — unified, structured, and ready to deploy to any digital channel.
Flamelink.io - Flamelink.io is a headless CMS for Firebase.
Comfortable - Content API for Websites & Apps
PushTable - Headless CMS for Google Firestore and Firebase
Strapi - Strapi is the most advanced Node.
FireCMS - An open source CMS/admin panel based on Firestore