ITEAD of Sonoff fame now sells a very inexpensive Zigbee USB dongle that should work out-of-the-box with both Zigbee2mqtt and the ZHA integration

Anyone interested in a new Zigbee USB dongle yet are not in a hurry might want to consider waiting for the expected upcoming Zigbee 3.0 USB Dongle from ITead based on Silicon Labs EFR32MG21 SoC