After the change serial number key I got the following message:
Device ID initialization must be performed from the debug board console.
Press 1 to set Serial Number now.
Pres X to abort setting Serial Number now.
If I press 1 it just gives a message that the screen will be cleared as soon as device ID initialization is complete, and just hangs until I restart. So some other piece of hardware is necessary to change the serial number. You can't do it from this utility.
Now, I wonder why they sell these motherboards if they can't be used? Should they have included a SIM card with the item, the one that's matched to the board?