Not quite an answer but I have used several Zigbee repeaters (Cheap ones from AliExpress, reflashed Sonoff Zigbee Bridge Pro reflashed with Tasmota - that was a pain and the Sonoff ZB Micro). I jsut plaster a few around the place to fully mesh the network and extend its range.
For ease I found the ZBMicro a great little device and increasingly useful as a USB switch. Even the AliExpress cheap ones have worked well. Far easier and not worth the effort in reflashing devices from my experience.
When I need more I will be purchasing the ZBMicro’s
After flashing the router firmware to the ZBDongle-P, you need to keep holding the Boot button, then press the RST button once, and finally release the Boot button.
The Dongle will enter pairing mode when the green light starts flashing.
The best way I have found of doing this is to put your thumbnail on the BOOT button then roll it onto the RST button (so BOOT and RST held at same time) then roll off the RST button, then off the BOOT button.