Use Dolphin to navigate through a samba share containing pictures, drag and drop some picture on desktop. A menu shows up, click "Set image" option. Nothing happens.
We use KIO to stat the file, which understands smb, but then we don't actually copy the file locally, so setting it doesn't work. Two options: 1.) Download the file into a temp folder and set it as wallpaper (difficult, especially getting the "when to delete it again" right) 2.) Disallow setting a non-local image as wallpaper (easy)
Option 1.5) Set the wallpaper to the SMB URL. Have it load it (using QNetworkAccessManagerFactory to make it speak KIO)
I can set an image from a samba share as wallpaper on Plasma 5.18. \o/ Operating System: Arch Linux KDE Plasma Version: 5.18.0 KDE Frameworks Version: 5.67.0 Qt Version: 5.14.1