configs/roles/config/tasks/plasma.yml

---
- name: Plasma | Set desktop wallpaper
  ansible.builtin.shell: |
    qdbus org.kde.plasmashell /PlasmaShell org.kde.PlasmaShell.evaluateScript "
                 desktops().forEach((d) => {
                     d.currentConfigGroup = [
                         'Wallpaper',
                         'org.kde.image',
                         'General',
                     ]
                     d.writeConfig('Image', 'file://{{ background_image }}')
                     d.writeConfig('FillMode', '1')
                     d.reloadConfig()
                 })
             "
  tags: config

- name: Plasma | Set Lockscreen wallpaper
  ansible.builtin.shell: |
    kwriteconfig6 --file ~/.config/kscreenlockerrc --group Greeter --group Wallpaper --group org.kde.image --group General --key Image '{{ background_image }}'
    kwriteconfig6 --file ~/.config/kscreenlockerrc --group Greeter --group Wallpaper --group org.kde.image --group General --key PreviewImage '{{ background_image }}'
    kwriteconfig6 --file ~/.config/kscreenlockerrc --group Greeter --group Wallpaper --group org.kde.image --group General --key FillMode '1'
  tags: config