↳ In-reply-to » Another thing that doesn’t work anymore after blocking network traffic from my Android phone: Some push notifications.

It looks like ntfy.sh can work either through the OS’s notification service or by maintaining its own connection to the server in the background. For privacy, you definitely want to use “Instant Delivery” and self-host the server.

https://docs.ntfy.sh/faq/#how-much-battery-does-the-android-app-use
https://docs.ntfy.sh/faq/#what-is-instant-delivery