I think the devices serial number should be hidden by default to allow users to prevent the leaking of identifiable information.

As they can choose obscure yet memorable usernames for the accounts of the TOTP authenticators, the only identifiable information that can't be hidden is the devices serial number.

I propose that a gesture detector should be added to the right of the serial number text UI, which toggles the visibility of the serial number when held down and the serial number label in the device picker be removed.