I’m not sure, I don’t know how it all this works. But from what I’m reading here: How do I Unify thread networks? , it seems that the older 1.3 Thread network (over the 1.4) allows for you to unify the Thread Network by making it the preferred network, but mostly with the help of Home Assistant or other similar methods and that would allow this to work. Most cases though they seem to only work with Main Hubs, not the Appliance based Hubs. Not only this, but it could be due to fact that all but Main Hubs (other then the new V4 Hubs) required to be connect to a network via an ethernet cable. But again, I’m not sure on how all this completely works, I just understand the basics.