Home Assistant SkyConnect - Home Assistant preorder is available now. But if you have a device that is currently, or will be updated to be, a border router is SkyConnect necessary?
For example, if you have an Amazon Echo device they are supposedto be updated to be a border router. Would those border routers share to other hubs like Home Assistant, or does Home Assistant also need to be a border router?
Standardized Thread border routers (those based on Thread 1.3 specification or newer) will allow any Thread device to connect, and will seamlessly route packets to the local area network (as connected via ethernet or Wifi).
A single Thread network can have more than one border router. If both are connected to the same LAN then they create a redundant path for Thread packets to reach the local network, such that packets can go through either. This is nice because it means if one border router goes offline for any reason (like getting unplugged, or a circuit breaker tripping) the Thread devices will remain accessible.
From a Matter perspective this is all true, except that at least once of your border routers must be Matter enabled and joined to your Matter fabric. This is required because to commission a Thread-based Matter device the commissioner must know the Thread network details. Thus it either must be the border router itself, or be able to ask a Matter-enabled border router for those details.
All of the major hubs that plan to offer Thread border router support should be Matter enabled. You should not even need to use Home Assistant to commission a Matter device, being able to comission it directly from say an Amazon Echo (4th generator or newer). If the device is in the same Matter fabric as Home Assistant, Home Assistant should automatically discover it.
Some minor details:
In theory one can also have thread border routers for the same thread network connected to two different local area networks. That is a complicated situation I won’t touch on further.
Matter also supports one Matter fabric having more than one different Thread networks connected. This is possible and supported, but would be an advanced scenario, and most users would want a single thread network for simplicity, and to make the thread mesh networking work better.