That's correct, due to China's ban on Google products (which includes Firebase Cloud Messaging) push notifications sent via traditional push SDKs will not deliver to Android devicesin China.
However, hybrid mobile engagement platforms such as that of OpenBack use edge computing to process data on individual devices, with no need to send data to a third-party cloud server. In this default mode, data is only transmitted between the device and the app backend, meaning it is fully compatible with China's firewall, as well as local data privacy laws.
If you would like some more information, you can check out this blog post: Accessing China's Mobile App Market: Overcoming the FCM Firewall
[Disclaimer: I am the blog manager for OpenBack.]
Best,
Anna