If you have a Displayport display, you can use a displayport to mini displayport cable, use switchresx, should work good.
If it's HDMI only, as the sibling pointed out the HDMI port won't work. However, Startech makes a displayport to HDMI adapter which works ( https://www.amazon.com/DisplayPort-HDMI-Adapter-Converter-60... ) (just make sure you get one which supports 4k60hz, most DP -> HDMI adapters don't).
If it's HDMI only, as the sibling pointed out the HDMI port won't work. However, Startech makes a displayport to HDMI adapter which works ( https://www.amazon.com/DisplayPort-HDMI-Adapter-Converter-60... ) (just make sure you get one which supports 4k60hz, most DP -> HDMI adapters don't).