The following products use the ASRock Z270 Fatal1ty motherboard, which has Displayport, HDMI and Thunderbolt 3 connectors. You can use the Thunderbolt 3 to HDMI adaptor (shown on the left) to enable a 3rd monitor. Tested with Windows 10 Home/Pro and Linux Mint 18.2 and Ubuntu 16.04.03

Add one to your order:
USB Type C (USB-C & Thunderbolt 3 Port Compatible) to 4K 60Hz HDMI Adapter

For Displayport to HDMI:
DisplayPort 1.2 to HDMI 2.0 4K/UHD 60Hz Active Adapter