It included adding the U2 256 Bits EEPROM to the U2 socket. UCM/Cbus1 has been shipped out with an empty U2 socket for some time
However if your UCM/Cbus2 does not have the U2 socket, then you should NOT try to solder a socket. This is not easy as the ic pin holes are filled with solder. Trying to remove the solder with a normal soldering iron may damage the PCB tracks. This requires special tools at the factory.
If the U2 socket is not present you should order a new UCM/Cbus
You can upgrade the ucm/cbus firmware to UCM/cbus2 even without the U2 eeprom, but in the Status field, it will show "EEPROM/Missing/Faulty" instead of "Normal/ No Error" as shown below