I used to use Rocket Chat a lot. One of the things they did was start to charge community servers for push notifications if it exceeded 10k a month. (I always thought that was pretty generous) It was something like $5 a month for 20k+ of notifications. Pretty good deal and you supported Rocket chat instead of hundred for an enterprise server account.
With Matrix and Element I am not quite sure I understand the push notification situation. Does folks behind element has a gratis push notification server up that we can really use for free? What are the limitis, etc. I donated to Matrix because I am using their software both the clients and the server. But I am just curious about this, because it was a none issue on Rocket chat for 10 years, and then it was.