Actually use the theme dark color for window background.

gpt4all-chat/main.qml

@@ -16,7 +16,6 @@ Window {
     minimumHeight: 480
     visible: true
     title: qsTr("GPT4All v") + Qt.application.version
-    color: "transparent"
 
     Theme {
         id: theme
@@ -25,6 +24,8 @@ Window {
     property var currentChat: LLM.chatListModel.currentChat
     property var chatModel: currentChat.chatModel
 
+    color: theme.backgroundDarkest
+
     // Startup code
     Component.onCompleted: {
         if (!LLM.compatHardware) {