I am getting the same issue.
I am also having issues with applications, if executed from the CLI, dropping the menu bar and not allowing foreground/background window switching.

This has only occurred after a full-upgrade to 2020.4
I initially thought it may be an NVIDIA video driver issue, but I have reloaded the drivers and kernel hooks, but this has not resolved the issue.

I am able to right-click on the background and get a terminal screen up.

Any help would be great.

Under the xfce4 settings there's a toggle for the desktop icon. Image of those settings.

image.png (105,176 bytes)   

image.png (105,176 bytes)   

if you have gnome then check for desktop icons extension

I am experiencing the same problem, did you solve it?

This question would be better asked on the forums