how to send a multicast command via MQTT?

ChirpStack (v4)
1

Sent a unicast command to a mote via MQTT is following I know:
topic: application/d92358eb-ba9b-4a36-8404-d17befc80467/device/fe03620000098761/command/down
{
“devEui”: “fe03620000098761”,
“confirmed”: true,
“fPort”: 10,
“data”: “MTIzNDU2YWJjZGVm”
}

how to sent a multicast command to many motes? how to set topic and json body?

2

I believe it’s only possible with gRPC, unfortunately.