The T6 Thermostat can be unregistered  by checking the following procedure:
  • Login into the Resideo app.
  • Tap on the thermostat's name.
  • Tap on the settings wheel (top right corner).
  • Select "Thermostat Configuration".
  • Select "Delete Thermostat" at the bottom.
A pop-up window will be displayed asking to confirm the deletion, select yes.