We implemented push notifications using FCM in chrome and firefox and it worked fine, but Safari doesn\'t support Service Workers which is mandatory for FCM.
Did any
I'm not sure about this new Safari and Service Workers situation, but I tried to implement FCM push-notifications in my iOS app and had to experience that you need an APN (Apple-Push-Notification) certificate first. I'm not sure if this is needed if you're working with Safari, but I could imagine that Apple also wants it's push notifications first to be redirected to the APN servers.