It is a good question but if it requires a signed firmware image to update the Silicon Labs EFR32MG21 SoC (Zigbee/Thread radio chip) then I assume that ITead/Sonoff are probably using the same chip model, pins mapping, and the very same signature as they used for Sonoff ZBBridge and ZB-GW03 (Eachen eWeLink ZbBridge Pro Ethernet Zigbee Gateway), as they would at least be able to use the exact same signed EmberZNet Zigbee NCP firmware image available from xsp1989 and Tasmota. Regardless I would believe that I can presume that ITead today currently ships Sonoff iHost with EmberZNet 6.10.3 based Zigbee NCP firmware image by default, and if so the Zigbee can probably be tested as-is without modification as long as hack the iHost operating-system for serial access to the Zigbee SoC (or ITead/Sonoff opens up serial access to the Zigbee SoC), or what do you think?