Review on 🌟 High-Quality StarTech.com Mini DisplayPort to HDMI Adapter for 4K 60Hz Video - Active mDP 1.4 to HDMI 2.0 Converter - Compatible with Mini DP or Thunderbolt 1/2 Mac/PC - Ideal for HDMI Monitor/TV/Display - mDP to HDMI Dongle (MDP2HD4K60S) by Micael Rau

I bought this to add a third external display to my mid 2015 15.5" Macbook Pro with discrete graphics. The old MBP with NVidia graphics was able to support three external displays simultaneously, but that's one of the consequences of Apple's switch about Radeon cards is that they only have enough power left to run two external displays at the same time using an "active" dongle (like this one) that allows you to get some power from the monitor instead of all that from the graphics card is coming. My third display is up and I love it!