Is there an open source, selfhosted analogue of Firebase Cloud messaging?

Question

Java

Actually, subject. An interesting project is compatible at the api level, which would allow not to make changes to all applications that need FCM, but to replace at the service level in android (from the client side), and from the backend - by replacing the request url.

Answer 1

does not exist

Answer 2

Only if analog, https://github.com/supabase/supabase .