You can connect using more than one device, but not at the same time.

The controller will pick up the first one it can find. So if you have multiple devices in the room compatible - turn Bluetooth off the ones you don't want to connect, so the only one available to be found is the right one.

Equally - if you're brewing on multiple G30s - then pair them up one at a time. So turn Bluetooth off all devices except the first one and turn on the right G30 and connect. Then turn on Bluetooth on the next device and turn the next G30 on and connect, and continue like that.