Thank you for contacting Plugable support! Sorry to hear about this issue. I’d be more than happy to assist you.
The UD-ULTC4K cannot support full features when being converted to USB 3.0. The dock requires USB-C to USB-C for full functionality with supported systems. When converting to USB 3.0, the HDMI port cannot function, nor can the dock support charging for a laptop. Unfortunately, we’re not aware of a USB-C switch that properly supports video, etc.
The USB ports, Ethernet, audio, and two DisplayPorts should still function however.
Please don’t hesitate to let us know of other questions.
Thanks again for contacting Plugable support and best wishes!