Right, but if you use ntfy.sh you can get proper mobile push notifications (instead of keeping the app running and using long polling or websockets).
If you use the public version of ntfy.sh then you don't need to do anything to set this up. If you self-host, you need your own Firebase Cloud Messaging (FCM) account and (for iOS) your own Apple Developer account so you can use APN.
Also the docs point out >Using Firebase is optional and only works if you modify and build your own Android .apk. For a self-hosted instance, it's easier to just not bother with FCM.
Who cares? Battery consumption of Gotify is negligible (it uses websockets). Same with CPU/RAM. What's the benefit of giving Google your notifications?
Personally I use FCM (Firebase push notifications) with a Capacitor plugin for push notifications, it works decently
Publicly hosted version is nearly useless if you'd like to use it to send notifications from your tiny workers/scripts/processes in the big datacentres - I have a minuscule worker in CF that needs to send one notification once every few days, and I *ALWAYS* get a 429. Always.
So this is good maybe if you're using it to sent from your laptop to your phone.