Dell Vostro 3400 with Type-C and WD19

 Hi @jphughan 

thanks for the detailed answer. Now it's clear

@Caezar93  One other thing to note is that MacBooks when connected to regular USB-C docks (as opposed to Thunderbolt docks) will only support a single external display, or multiple displays only in mirrored mode, not Extend mode.  This is because macOS does not support DisplayPort MST.  If you want to run multiple displays from a dock with a Mac, you need a Thunderbolt dock.  But the brand new MacBook systems with the M1 chip only support a single external display no matter what.

@Caezar93  In order to use the display outputs on the WD19, the source system needs to support video output, i.e. DisplayPort Alt Mode, over USB-C.  That is an optional capability on USB-C ports and therefore not all systems with USB-C ports support it.  And in order for the WD19 to provide power to the attached system, the system must support being charged via USB-C.  That is also an optional capability.  The Ports and Connectors section of the Vostro 3400 Setup and Specifications document (link) mentions an optional USB 3.2 Gen 1 Type-C port.  Typically when a Dell laptop has a USB-C port that supports video and/or charging, that capability is specifically mentioned.  Since there is nothing like that in the specifications, the USB-C port might be a data-only port, without any support for video or charging.  I don't know for sure, but that's typically how it works with Dell documentation.  Also note that Dell's Docking Station Compatibility Guide here only mentions Vostro 5000 and 7000 Series systems, so it's possible that the Vostro 3000 Series systems don't get these optional capabilities.