Trying to set desktop background to a jpg file, but when I select the folder (left click on a spot where there is no icon on the desktop > select "Desktop settings" > lower left area there is "Folder:" > and next to it drop down list > click on "Other" > opens up "Select folder" file-browser window) files are grayed out. When I click "Open" it goes back to Desktop settings window and nothing is showing in Background tab. I searched the internet, and none of the answers seem to work. I have not tried yet the command line method. This is xubuntu, 18.04, xfce.