hodlbod on Nostr: I haven't dug into the details on any of this, but the way I understand it is (at ...

I haven't dug into the details on any of this, but the way I understand it is (at least when using FCM) you generate a client-specific token and send it to the push relay, which then sends notifications for all subscriptions by token. So you wouldn't need a relay per client, or per user (unless the user wanted to set up a custom push server).