Misleading plugin page. It says the plugin is called "Image ALT", but what actually installs is called "Visual ARIA". It doesn't show only alt tags as the screenshot displays, but instead all kinds of accessible name and description tags (one of which is the alt) that can only be toggled together, and they show above/below the images, not overlaid.

Edit: installed the 2019 version instead, and that mostly works as advertised.