Update: I found another possible solution on the Nvidia forums: Delete the file ~/.config/xfce4/xfconf/xfce-perchannel-xml/displays.xml.
I have the same issue and narrowed it down to the Composition Pipeline setting. When it is enabled, the XFCE desktop does not become visible, but instead the LightDM background stays on screen. Switching between TTY forces ...
There might be an issue with the lightdm-deepin-greeter.
Install an alternative greeter, e.g lightdm-gtk-greeter
sudo pacman -S lightdm-gtk-greeter
Then edit /etc/lightdm/lightdm.conf
sudo nano /etc/lightdm/lightdm.conf
Look for the line that is like
greeter-session=lightdm-deepin-greeter or the value could be something else
change it to