I think it will show thumbnails for folders by default in 18.04. But when I hover over the files
icon, even with 2 folders open, I do not see a thumbnail. Not just folders, it does not show thumbnails for Firefox, Terminal or Gnome Clocks. I think it is safe to say that thumbnail preview is not available on my 18.04.
Is it normal ? Is there any method through which I can enable thumbnail preview ? Thanks.