The UDC firmware is provided by https://www.igel.com. The download path depends on the exact version to be used.

 To download the firmware for UDC3, go to https://www.igel.com/software-downloads/software-downloads-former-universal-desktop-and-legacy-versions/ > OS 10 & V5 > Universal Desktop Converter 3 (OS 10) (STICK).

To download the firmware for UDC2, go to https://www.igel.com/software-downloads/software-downloads-former-universal-desktop-and-legacy-versions/ > OS 10 & V5 > Universal Desktop Converter 2 (V5) (STICK).