Note that it looks like he had to first manually reflash the Silicon Labs EFR32 Zigbee chip with another firmware image (using a USB Serial Flasher / USB to TTL Programmer) in order to make the Zigbee Coordinator compatible with Z2M’s EZSP adapter, which is something that is listed as experimental (or “beta” stage) for Zigbee2MQTT as support for Silabs EZSP adapter code is still in the relatively early development in the zigbee-herdsman libary that it depends on, (and is in need of additional testers and developers before it will become more mature), see → https://github.com/Koenkk/zigbee-herdsman/issues/319