Change the background colour in compact mode to achieve the same level of contrast as with bubbles.

src/qml/Component/Timeline/SectionDelegate.qml

@@ -42,6 +42,6 @@ QQC2.ItemDelegate {
     background: Rectangle {
         color: Config.blur ? "transparent" : Kirigami.Theme.backgroundColor
         Kirigami.Theme.inherit: false
-        Kirigami.Theme.colorSet: Kirigami.Theme.Window
+        Kirigami.Theme.colorSet: Config.compactLayout ? Kirigami.Theme.View : Kirigami.Theme.Window
     }
 }

src/qml/Page/RoomPage.qml

@@ -581,8 +581,12 @@ Kirigami.ScrollablePage {
         }
     }
 
-    background: FancyEffectsContainer {
+    background: Rectangle {
+        color: Config.compactLayout ? Kirigami.Theme.backgroundColor : "transparent"
+
+        FancyEffectsContainer {
             id: fancyEffectsContainer
+            anchors.fill: parent
             z: 100
 
             enabled: Config.showFancyEffects
@@ -615,6 +619,7 @@ Kirigami.ScrollablePage {
                 }
             }
         }
+    }
 
 
     function warning(title, message) {