How do I set Learning Apps as default starter Apps?
You can set any Learning App as a default starter App as soon as the App is published.
Once you have selected the published Learning App from the All Published Apps tab on your Learning App Author page, click the orange Apply box next to "Make this a default starter App":

Once you have clicked the Apply box, this Learning App will automatically show up on a any new Community member's Learning Path at first sign-in.