Default to mobile app promotion

interface_config.js

     REMOTE_THUMBNAIL_RATIO: 1, //1:1
     // Documentation reference for the live streaming feature.
     LIVE_STREAMING_HELP_LINK: "https://jitsi.org/live",
-    // Enabling mobile landing page with the link to mobile app.
-    MOBILE_APP_ENABLED: true
+
+    /**
+     * Whether the mobile app Jitsi Meet is to be promoted to participants
+     * attempting to join a conference in a mobile Web browser. If undefined,
+     * default to true.
+     *
+     * @type {boolean}
+     */
+    MOBILE_APP_PROMO: true
 };

react/features/base/util/interceptComponent.js

         const OS = Platform.OS;
 
         if (OS === 'android' || OS === 'ios') {
+            const mobileAppPromo
+                = typeof interfaceConfig === 'object'
+                    && interfaceConfig.MOBILE_APP_PROMO;
+
             return (
-                interfaceConfig.MOBILE_APP_ENABLED
+                typeof mobileAppPromo === 'undefined' || Boolean(mobileAppPromo)
                     ? UnsupportedMobileBrowser
                     : NoMobileApp);
         }