In AWS Greengrass v2 developer guide, Move from AWS IoT Greengrass Version 1, it says, AWS IoT Greengrass V2 currently doesn't support connected devices, also called Greengrass devices.
Wonder what would be the recommended ways (for the time being) to connect edge devices, such as ESP devices, to the Greengrass core device running Greengrass version 2.
Found on AWS IoT forum an explanation from Farad at AWS in Feb 2021:
Greengrass V2 unfortunately does not provide GGAD (Greengrass Aware Device) yet. They are actively working on addressing this gap and hope to release it in the coming months. Until that time, you can use Greengrass version 1 or you could use this example MQTT Bridge code for Greengrass V2 as a skeleton for implementing your own MQTT broker on V2 in order to support remote devices.