Some of ITEAD Studio's Sonoff home automation devices include Zigbee connectivity with for instance Sonoff BASICZBR3 smart switch or a version of Sonoff S31 smart socket with integrated Zigbee.
Those devices usually work via a Zigbee enabled gateway that could be a router, Raspberry Pi SBC, or mini PC, which ITEAD did not offer so far. But to help people making their own Zigbee gateway the company is now selling a low-cost ($3.99) CC2531 USB dongle preloaded with CC2531ZNP-Prod firmware, and compatible with Zigbee2MQTT open-source Zigbee to MQTT bridge once plugged into a PC, Raspberry Pi, or another