Comment by SushiHippie

Sure, just wanted to tell you about it, as this seems to be defacto standard for foss android apps, for example most if not all https://matrix.org clients use it for push notifications (when you use their de googled build, or don't have play services) available. I also use a Signal fork with UnifiedPush and have some server alert scripts which post to my self-hosted ntfy instance, and the ntfy app itself will display them (otherwise for the Messengers, the Notifications will be from the messenger app itself, as these apps get "notified" aboout a notification and then do their own thing).