The Popups gadget, T164044 Navigational popups and page previews, is usefull to see a short description, and use some features, when any user mouse-flying upon links, without clic upon links, in many pages.
Then it becomes the Hovercards Beta Feature T70860.
The right and attended feature is the display of a pop-up short description.
To see this task we can compare in 2 wikis this Popups gadget.
To see this task we can also compare in 2 wikis this Hovercards Beta Feature.
You can compare in fr.wikipedia and in fr.wikisource or other languages. In each:
In your preferences, desactivate and valid, then activate and valid the Popups gadget (or the Hovercards Beta Feature)
Then try to "fly the mouse" = "hovercraft" without clic upon links.
In the last MediaWiki 1.29.0-wmf.21 (rMW29800e6e5329) the feature run right like attended in fr.wikisource but not in fr.wikipedia.