If you are contemplating migrating from Google IoT before it retires in a year, you
might want to use MIMIC MQTT Simulator and its SaaS offering for Google IoT
https://mqttlab.iotsim.io/gcp to design / develop / test your migration strategy.
MIMIC MQTT Simulator allows you to simulate a large number of your assets that
connect to Google IoT Core, then migrate them to the alternative of your choice.
You can duplicate your current IoT environment in MIMIC to make sure the new
IoT platform handles your specific requirements.