? I think I'm misunderstanding your comment. This replaces the entire push notification infrastructure.

The "distributor" receives notifications onto the device and sends them to the apps via a standardized API.

The apps themselves then post the notifications to the user via the android on-device notification API.

The "gateway" receives the notifications from the services over a standardized API and sends them to the distributor.

How the gateways actually distribute the notifications is actually completely up to the gateways. The main gateway (ntfy) uses websocket, another (nextpush) piggybacks off of nextcloud, and the new kid on the block (sunup) uses the Mozilla Push Service behind the scenes.

Nothing in this is restricted or locked in to a centralised platform.