You probably have the receipt for the service at the dealer. Look at it and see if there is reference to the item replaced. They probably did not replace the screen with a 2020 version because 3.0.19205 would not support the drivers needed to make it work. I have a theory that you had a theme selected that is discontinued in Sync 3.4 and that is the reason the screen is black. Unfortunately, it will require FORScan or Ford IDS to fix it.
I have something you can try to find out if this is the case. Run the APIM Interrogator Utility. You won’t be able to see anything, but I would bet the APIM is running. Leave the usb inserted for at least 3 minutes, then remove it and look on the usb for the xml file mentioned in the tutorial. If the APIM is running, the xml will be on the usb, if it is not, it doesn’t mean it’s totally dead, but you will need to access the unit with FORScan or other tool.
Tutorial: Tutorial: APIM Interrogator Utility - Ford / Guides & Info - CyanLabs Official Community
Do you still have audio and can adjust the volume? And tune stations?