How can i read the printed serial number from the physical key or from the app/cli without typing the pin?
There is not a unique serial number that can be read. This is intentional as to not permit tracking users. If you would like to assign keys a unique number you could assign a serial number in the label slot but this would required unlocking key.
without sn id, it could be not very convenient when using multiple onlykeys.
What use case are you looking for here? Maybe there is another feature that could be used.
such as family use case, different onlykey for different member, but usually the keys are left together on the table, and not easily distinguish them.
For this using different color cases may work well. Or you could add asset tracking stickers/labels with a label maker.