In Settings>Background when “Add Picture” is clicked my Pictures folder opens and lists all the pictures and subdirectories there however when I click on a picture it will not activate it as the new background (or at all). Otherwise, double click on a picture opens it in GThumb without any problem.
I did install a new WM to try out briefly but have now removed it entirely. Could that have switched something?
Perhaps. Previously it was always able to use a picture from any chosen folder. In any case, the picture I want to use as background is already in /usr/share/backgrounds/manjaro-budgie.