For my other project I needed a way to get data in Firestore. There is FireCMS or Flamelink, but I was very unhappy with those solutions.
So I decided to built my own headless CMS. It's very minimal and lightweight. It uses a simplified version of the FireCMS data models and can derive them from existing data. However, handling sub-collections, editing content, and managing storage content is easier.
It's a SPA with PWA support written in Svelte 4 and runs fully in the browser (no backend). Metadata models is stored directly in your Firestore (as __schema). For now they can be edited as JSON only.
If you want to play around, you can use the firebase emulator suite too.
More infos at github or check out the online live demo: https://fl-cms.web.app
Important note: ATM it's released as a MVP. Working with it possible but not all eventualities are implemented yet since the other projects must go on too.