Gotify/server: A simple server for sending and receiving messages in real-time
github.com
github.com
Here's the thing I banged together to pipe Zulip events into notifications. There are a bunch of nice things I could add to it, but I haven't had enough need to do so yet.
Without GCM though, every app needs to maintain a separate connection, which drains more battery.
That's why we need more alternatives to GCM, like UnifiedPush.
(Android, Samsung S20+)
I've wanted something like this for quite a while but instead I've been mainly using webhooks/bots to Slack/Matrix/Mattermost for this.
Both support simple http APIs to trigger push notifications to iOS as well as other platforms. Both options worked great for me when I needed them.
You otherwise get an Android phone.