Do the GEN2 6, 12, and 18 port Hubs need to be connected to external power to work?

All 3 models (HD-G206, HD-G212, HD-G218) can be bus-powered by the USB-C device (iPad Pro, MacBook, laptop, etc.) and do not require external power to work. They can also be powered by an external USB-C PD power supply. In the case of the 18-port, there is also an option to use an optional DC power supply. Once externally powered, the hubs will provide power pass-through charging to the USB-C device.