In Firefox 131, try going to Tools -> Settings -> General Tab and see if Show an image preview when you hover on a tab is checked in the Tabs section. If so, uncheck it.

No, it is not checked. And there's no check in the box for "show tab previews in task bar."

Seems this is a new feature of 131. But there's no way to get rid of it.

Type about:config into the search/URL bar.

That will bring up a warning which you'll have to acknowledge.

On the next screen there's a search box at the top. Type or paste browser.tabs.hoverPreview.enabled. That will then appear below with the word true next to it. Double-click true and it will change to false.

Thanks, that worked.