Knowledge Base Help & Documentation:
Why all articles are featured after migration to Joomla?
This is due to the fact that if not featured, the articles won’t be visible on the front-end of your Joomla website because of the peculiarities of Joomla article management.
You can easily turn off “Featured” on certain articles. For this, within your Joomla Administration panel, go to Content -> Articles Manager, select the needed article and click on the star next to it.