You can use this plugin https://wordpress.org/plugins/quick-featured-images/
In description it says "You can also see posts with no featured image at a glance."
But from code side, wordpress manages images, documents any media by creating an attachment post for holding the information about that media and it's relation (if any) with other post/posts, which means you need sql query to find all posts without any images attached. To retrieve all posts without any image attached you can execute a query like this:
SELECT DISTINCT(p.ID), p.post_title, p.post_content FROM `wp_posts` p
LEFT JOIN wp_posts im ON p.ID = im.post_parent AND im.post_type = "attachment"
WHERE p.post_status ='publish'
AND p.post_type = "post"
AND im.ID IS NULL
AND p.post_content NOT REGEXP 'src=".*"'
last code will remove posts which includes images inside it.