I was trying to get push notifications to work. I am running Unity + GS + Android. From the FCM tutorial it looks like its a request that is initiated from the app or client and then I need to setup GS to respond to that ? Is there a way where I can broadcast a push notification from GS (and not be it a part of Request/Response ?)
This would require a lot of custom setup.
Firstly, you need to create a custom player collection. You can see how to do this at the start of the tutorial here.
Once youve got this list you can query player however you want to get a list of ID. You would then pass those IDs into a bulk-job so you can send as many messages as you want.
I cant tell you where you'd need to run the code from. I'd need to know what you intend to send to the players to advise you further on that.