You don't, there's privacy respecting ways of delivering notifications in android.

Also, a 24/7 connection to a server isn't nearly as bad as you might think.

The connection isn't active the whole time, it only uses any significant amount of battery if there's actually data being sent or received. You likely already have quite a few of them anyway, how do you think systems normally listen for push notifications?

Besides all that, I read in other comments that the privacy issue was the device id firebase needs. Obviously apple also needs some kind of device id, otherwise how do they know where the notifications are going?

Did some searching, yup apple also needs a unique identifier:

When it’s time to send a notification, you generate a request that contains the notification data and a unique identifier for the user’s device.

From https://developer.apple.com/documentation/usernotifications/setting-up-a-remote-notification-server