I have a Google Chrome Extension that listens for GCM messages in a background script via
chrome.gcm.onMessage.addListener. Our provider is planning to upgrade their infrastructure to use the latest Firebase Cloud Messaging which is no longer compatible with GCM. We’ve confirmed the gcm addListener API no longer receives messages after upgrading to FCM in the dev environment.
I’ve found migration guides for Android, iOS, and progressive web apps but none specifically for background scripts in Chrome extensions.
Some resources I’ve found: