Gnoppix KDE: Wallpaper preview isnt showing

Issues and Help
1

How to fix:

  1. Installed kio-extras provides the thumbnail KIO slave (thumbnail.so) that Plasma uses to generate wallpaper previews
  2. Cleared thumbnail cache rm -rf \~/.cache/thumbnails/\* \~/.cache/plasma\*
  3. Increased thumbnail size limits created ~/.config/kioslaverc with:
   [Thumbnail\] 
   MaximumSize=100000000 
   MaximumRemoteSize=100000000

On your KDE desktop now run:

pkill plasmashell && plasmashell --replace &

This allows thumbnails for large wallpapers (e.g., 6016×6016 = 36MP images) while those big images also block the smaller one.

After running the restart command on your desktop, open System Settings → Appearance → Wallpaper → previews should now appear.