Both Monal and Conversations support XEP-0357. Each project runs their own XMPP-to-Apple/Google gateway for push notifications. It has to be that way because th

Both Monal and Conversations support XEP-0357. Each project runs their own XMPP-to-Apple/Google gateway for push notifications. It has to be that way because the gateway server and client phone application have to be signed by the same developer account. The client phone app tells your XMPP server which gateway to use (or maybe it's vice-versa, the gateway contacts your server. I forget). In any event XMPP servers like Prosody support this out-of-the-box.