Can they use https://unifiedpush.org/ on Android (as an option, not insread of FCM)?

You could certainly propose it to them (especially with a PR that includes code), or patch it into your local copy if they decline. I wouldn’t be surprised if Google wouldn’t allow that in the Play Store-compiled version of the app, but I don’t know.

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notpushkin 12 hours ago | parent [-]

Yeah, I think it’s quite common to have a “Google Play version” and an “F-Droid version” with different implementations behind build flags. Not sure if it’s required though – I can see some UnifiedPush providers in the Play Store, at least.

	▲	jkaplowitz 3 hours ago \| parent [-]
		As I said, I don’t know whether Google minds UnifiedPush or not. Maybe they don’t.