Description: Use com.lomiri.Shell(.Greeter) as GSettings storage place.
Author: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
Forwarded: https://gitlab.com/ubports/development/core/lomiri/-/merge_requests/138

--- a/qml/Shell.qml
+++ b/qml/Shell.qml
@@ -193,12 +193,12 @@
 
         GSettings {
             id: backgroundSettings
-            schema.id: "org.gnome.desktop.background"
+            schema.id: ((shell.showingGreeter == true) || (shell.mode === "full-greeter") || (shell.mode === "greeter")) ? "com.lomiri.Shell.Greeter" : "com.lomiri.Shell"
         }
 
         candidates: [
             AccountsService.backgroundFile,
-            backgroundSettings.pictureUri,
+            backgroundSettings.backgroundPictureUri,
             defaultBackground
         ]
     }