Update loses desktop

Try the following:

1 - first go into the Finder's Sidebar settings and make sure iCloud Drive is checked.

2 - open a new Finder window and click on iCloud drive in the sidebar.

If you get the iCloud drive and folders for both your Desktop and Documents folders you've inadvertently enabled iCloud drive and Documents & Desktop during the update. It's usually asked during an upgrade, not an update.

If you do find that you have that enabled you can go into the System/Apple ID/iCloud/iCloud Drive settings pane and disable the two folders. You'll be asked if you want to keep copies on your Mac.

Found this on an older thread, if you are running Parallels and using an external monitor. Recently all my desktop files disappeared when my laptop is connected to an external monitor. Turns out Parallels Tools for Mac has a 'Presentation Mode' which hides all the files on the desktop - not just on the monitor, but also when you check Desktop folder. Not sure why, but they reappear when you uncheck Presentation mode. Maybe that helps