Doubt this will fix anything, but worth a go

Main.qml

@@ -4,9 +4,9 @@
     SPDX-License-Identifier: LGPL-2.0-or-later
 */
 
-import QtQuick 2.15
+import QtQuick
-import QtQuick.Layouts 1.15
+import QtQuick.Layouts
-import QtQuick.Controls 2.15
+import QtQuick.Controls
 
 Item {
     id: mainStack
@@ -18,8 +18,7 @@ Item {
         id: sceneImageBackground
         source: "background.png"
         anchors.fill: parent
-        sourceSize.width: parent.width
+        sourceSize: Qt.size(parent.width, parent.height)
-        sourceSize.height: parent.height
         fillMode: Image.PreserveAspectCrop
         smooth: true;
     }
@@ -37,9 +36,7 @@ Item {
             leftMargin: 10
         }
         height: 50
-        background: Rectangle {
+        background: null
-            color: "transparent"
-        }
         font.family: "Rajdhani"
         font.capitalization: Font.AllUppercase
         font.bold: true
@@ -129,9 +126,7 @@ Item {
                 y: 5
                 width: 955
                 height: 75
-                background: Rectangle {
+                background: null
-                    color: "transparent"
-                }
                 font.family: "Rajdhani"
                 font.pointSize: 30
                 font.bold: true
@@ -163,9 +158,7 @@ Item {
                 y: 5
                 width: 955
                 height: 75
-                background: Rectangle {
+                background: null
-                    color: "transparent"
-                }
                 font.family: "Rajdhani"
                 font.pointSize: 30
                 font.bold: true
@@ -175,7 +168,6 @@ Item {
                 onAccepted: {
                     attemptingToLogin = true
                     sddm.login(usernameField.text, passwordField.text, session.index)
-                    event.accepted = true
                 }
             }