So I managed to kill mine by following the steps at https://medium.com/@karthikb23/revive-your-moto-360-gen-1-2020-updates-659d92d9cafd while trying to get it to update some apps. It would boot to the “Starting Android App 1 of 1” and go no further.
The method was to place it on the charger, and hold down the power button until it turned off, then hold it down again to turn on into a recovery mode. From there a factory reset by pressing the button and swiping to select the relevant option.