I know that the Thread standard/protocol support using multiple Thread Border Router (TBR) as entry/exit points for a single Thread network, but as I understand this is not yet supported with ZBT-2 nor with the built-in OpenThread Border Router (OTBR) add-on/integration in Home Assistant, or does it support that already?
I think that the OpenThread Border Router (OTBR) add-on/integration is currenty limited in this regard so today it can only connect to a single Thread Border Router, or am I wrong?
…I bet that if it supported multiple Thread Border Router then they sell a lot more of ZBT-2 as the more Thread Border Router devices your network have the more stable and robust it will be! 
I believe to achieve that Home Assistant developers would both need to add support to connect multiple OpenThread Border Routers to the OpenThread Border Router (OTBR) add-on/integration, and ESPHome firmware developers probably also need to enable Wi-Fi support on the ESP32 in the ZBT-2 so that it can act a LAN-proxy to allow connecting remotley to the OpenThread RCP firmware.
The architecture would look something like this:
- Home Assistant’s OTBR add-on/integration ↔ LAN ↔ ESP32 proxy ↔ OpenThread RCP.
PS: FYI, both ZHA/zigpy and Zigbee2MQTT/zigbee-herdsman developers have by the way been working on experimental Zigbee stacks that can achieve a somewhat similar architecture for Zigbee using a concept they call “Zigbee-on-Host” (solutions that also make use of OpenThread RCP firmware on the adapter though with the limitation on only using one adapter at a time but since the Zigbee stack is broken out you could have a active-passive High Availability setup that can fail-over to a other OpenThread RCP adapter if one adapter breaks). You can check those out here: