The Home Assistant Connect ZBT-1 ships with a full-fledged Zigbee firmware. At this point, there are no known issues with the factory-flashed firmware.
Firmware updates for the Home Assistant Connect ZBT-1 are natively supported in Home Assistant 2025.4 and newer if you are running the Zigbee Home Automation integration or OTBR integration. If there is a new firmware update available, you will see an update notification.
If you want to switch from the Zigbee to the Thread firmware, follow the steps on Switching from Zigbee to Thread.