ra-supabase VS API Platform

Alternatively, ra-supabase (https://github.com/marmelab/ra-supabase) is an adapter for React-Admin which allows it to hook into Supabase.

Probably API-platform. The website is down at the moment, but: https://github.com/api-platform/api-platform It's Symfony based (and plays nice in that ecosystem), also allows you to describe entities via Schema org vocab, has a client generator, and comes with docker-compose and helm charts. I've used it extensively to build various headless services. It's really easy to expose annotated Doctrine entities.

API Platform is a framework for API-first projects, built on top of Symfony components. Let's see how to create a minimal and lightweight starter project in just 5 minutes!

Just use a nice framework like Symfony and for an API there is a nice thing called API Platform

On the Symfony side, a headless API can be built really quickly with https://api-platform.com/. You describe your domain entities with Schema.org vocabulary, can use a client generator to hammer out a UI in Next, Nuxt, Quasar, or whatever as a starter, it comes with an admin backend, and a Helm chart to deploy on Kubernetes. Works great for APIs when paired with, say Nuxt SSGs/PWAs if you want more of a JAMstack approach.

It could be implemented with STOMP, or Mercure (goes well with API-Platform, written in PHP/Symfony), you could write your own with the help of nchan and scale it via Redis. If it's a web service, the best practices for operating and scaling are well established, Godot then just becomes another client.

Why would someone use this over API Platform?

That looks like out-of-the-box api-platform. It even auto-updates the data on screen, no JS needed. Pretty powerful stuff and if it can be done in PHP, it can be done in other language.