"Declarative Web Push" is a web browser javascript API to subscribe to events from an HTTP server. It is similar to the "Web Push" API but changed to be better for mobile devices in a few ways.
Both the old Web Push and this new Declarative Web Push APIs use "the same Apple Push Notification service that powers native push on all Apple devices". I don't know if that means an Apple server actually listens for the notification from the HTTP server or if the device itself maintains the connection to the server.
It seems that for iOS this API only works on websites that are pinned to the home screen (i.e. not a notification from a site open in safari as a browser). These pinned websites work more like apps.
Is there something similar like this on Android? Either for pinned apps or from the browser? In other words, is there a reliable and efficient way to get notifications to an android phone without having to sign up for any service?