I have a fresh install of Elementary Juno on a Lenovo laptop with an HDMI port. If I plug in an HDMI cable -- doesn't matter if there's a signal down it or anything -- then my screen goes black and show an unreadable error. If I unplug the cable, I get the Elementary desktop again, but there's no OS UI (Applications and search in upper left, battery power/other icons in the right, dock, etc). I am able to pull up the terminal via keyboard shortcuts and do things from the shell normally.
a- what the heck do I need to do to fix my HDMI port? I'd like to connect to an external monitor.
b- how do I restart the desktop UI from the cli?