ZBT-2 Unable to onboard New Zigbee Devices

I have had a ZBT-2 up and running for about 10 days, and today I tried to add my old re-flashed Sonoff Type E dongle as a router.
Flashed as:
Current Device:
ZBDongle-E
Current FW:
Zigbee Router 8.0.2

When the Sonoff is plugged into a usb port the only device found is the ZBT-2:

This appear similar to https://github.com/home-assistant/core/issues/155228

Has anyone had issues onboarding new ZB devices with the ZBT-2?

Not 100% sure what happens under the hood, but if the migration process clones the previous coordinator’s IEEE address, then you can’t ever use it as a router.
Basically (assuming what I suspect is true), you currently have 2 devices with the same address which will lead to a bad time if they are part of the same network.

The only options you have in this case are:

  • Check if it’s possible to overwrite the address on your old dongle.
  • Sell it & use the money to buy another router.

Well that makes perfect sense, thanks at least I will not waste time trying to solve a non issue.