2016 Carnival Platinum and 2018 Stinger GT
This is identical to my issue, reboot of power used to fix it. Now nothing. Still no ETA for me from dealer.Mine just died, the behaviour is identical to that described at the start of this thread.
It's fairly desirable to have the head unit working. Without it there's no navigation, no multimedia (Bluetooth, radio, etc), no parking cameras, you can't see any of the climate control settings (for all I know it works, but you can't see what temperature you're on or anything like that). The parking sensors still work (the display for that is in the instrument cluster).
Previous to this I've had a few cases where I needed to "reboot" the car (turn it off, lock it, then hop back in) to get the head unit working again, and some slightly irritating software bugs.