You can use a USB c to hdmi dongle or hub, it will lunch dex auto or simply slide the notification bar to activate. This is the one I got from Amazon and has worked without issue.

Check this out at Amazon USB C to HDMI Adapter, USB 3.1 Type C Hub to Digital AV Multiport Adapter with 4K Output, USB 3.0 Port and Charging Port Compatible with Mac-Book Compatible with Hua-wei Mate 20, Note 9, S9 and More https://www.amazon.com/dp/B089Q83TPQ/ref=cm_sw_r_apan_glt_fabc_AW0CP77NC9P48ETVVNRF?_encoding=UTF8&psc=1