I really like using Pushover[0] for this stuff. The app on iOS is really great, including ability to include images and custom icons in the (native) push notifications, custom sounds, punching through silent mode for emergency alerts and even custom actions I believe (haven’t used the latter).

I’ve toyed with doing something with Signal but the Pushover route has always felt a bit better suited for my use case.

The custom icons are particularly handy as I get push notifications from all sorts of systems (from home automation to GitHub Actions) and it’s really easy to see at a glance where the notification is coming from.

Good luck with your project!

[0] https://pushover.net

Looks interesting, will check that out!