There is also a very useful Human skill present in the developed Society, called reading:
OP mentioned needing to provide the Serial for the Device which i do not have / or at least not knowingly. As far as i know there is no ledgible Serial on the Device Outside, no more Original Packaging, nor a Serial Number displayed on the default landingpage from the WebUI without password.
Mind you i did read the linked artikle before posting - though realised, that without the serial, as mentioned in the Heading of this post, there is a high likelyhood of needing to find a diffrent solution of A extracting a Serial from the Device or B resetting the password of some sort.