It does work fine on Firefox on Android, but we don’t support that browser. It works because it adheres to the same web standard every modern browser implements.
iOS Safari browser don’t implement the Web Push Notification web standard, so there is nothing we can do here.
That plugin only “unhides” the web push button for desktop browsers. Support is still the same, Chrome, Firefox & Edge, on the Desktop and Android. We only hide this button on desktop because most people don’t want notifications when the browser is closed on the desktop (and you are playing a game, fullscreen and dies because of the notification lag 
).