I can confirm that the above command does not work. The command that works for me is
gsettings set org.gnome.desktop.background picture-uri file:///direct-picture-path
gsettings spits out an error when I type in the command without 'picture-uri' as you suggest.
I can confirm that the above command does not work. The command that works for me is
gsettings set org.gnome. desktop. background picture-uri file:// /direct- picture- path
gsettings spits out an error when I type in the command without 'picture-uri' as you suggest.