Too bad ITead didn’t add SMA (or IPEX) connector + external antenna or used a ceramic chip antenna.
Solder points for PCB trace antenna look too small for an average DIY thinker like myself for soldering on a RG316 SMA-Female to PCB solder pigtail antenna cable, but maybe others are willing to do it?
There are guides to solder SMA connector PCB trace antenna path so can use external antenna, ex:
https://www.instructables.com/External-Antenna-for-ESP8266/
https://community.home-assistant.io/t/how-to-add-an-external-antenna-to-an-esp-board/131601
https://community.openhab.org/t/esp8266-antenna-mod-extend-wifi-range/78982
Most of those guides use RG316 SMA-Female to PCB solder pigtail cable and a 2.4GHz WiFi antenna:
https://www.amazon.com/Pigtail-Antenna-Extension-Connector-Lsgoodcare/dp/B072LFYHHN
Note that there are of couse a huge difference in quality between different external antennas for Zigbee:
PS: New dongles with only integrated antenna should use a ceramic antenna, not a PCB trace antenna.