homeassistant

I can't say how using 2 ZBT-1's at the same time will work out but I can say they work great for Thread/Matter.

There shouldn't be an issue getting both up running as long as you know which ZBT-1 is assigned to which port.

I never had any luck with zigbee USB dongles. All my devices would just continually fall over and it was a massive pain getting them back talking. Someone ended up recommending me the Zigstar UZG-1 which is a network Poe device, and I have never had a problem since. It has been up and problem free now for about half a year.

As it isn’t plugged into your device, you should also eliminate the issue trying to get it to work in docker

Vaguely remember that the dual stack firmware wasn't being developed anymore and was deprecated.

I only have the one ZBT-1 at the moment, but like you I was also thinking about getting a second for Thread (though in the form of a HA Yellow). There's this bit in the documentation for the Yellow about multiprotocol support and one of the things is that it's better to have a second wireless chip in some cases which I take to mean that you can have multiple ZBT-1, one for Zigbee and one for Thread.

For large networks it is advisable to add a second wireless chip. This allows to run Zigbee and Thread each on a dedicated wireless chip and on separate channels.

(source: https://yellow.home-assistant.io/guides/about-multiprotocol/)