Only one monitor showing

[rboerner]

Originally Posted by Froggiess

Hello:

I have a Lenovo thunderbolt 3 dock with a MacBook Pro. I have two DisplayPort to HDMI monitors connected to the dock. The Macbook connects to the monitors without an issue. However, the desktop is mirrored on both (basically as if it was one monitor) and there is no option to extend to these two additional displays. Under System Preferences / Monitors it only shows one. Is there a setting somewhere that I am missing?

This works fine with a Windows machine.

A quick note up front, the dock you mention does not have DisplayLink technology inside of it, so DisplayLink will not be able to assist.

That said, based on your description of the behavior it would appear that the Lenovo Thunderbolt 3 dock has what is known as a DisplayPort multi-stream hub inside of it (also known as DisplayPort MST) to drive both of the video outputs.

DisplayPort MST hubs are not supported on macOS. When a DisplayPort MST hub is connected to a macOS system, all of the connected displays will be 'mirrored' and seen as one physical display as you describe.

In short, the behavior you are seeing is the result of a limitation within macOS and unfortunately there is no workaround.