browser.tabs.hoverPreview.enabled = false will make Firefox work how it used to, ie display a small pop-up with the full name of the tab. I don't know how that can be removed.

If you want NOTHING to show when hovering on a tab you'll have to use custom CSS so it's up to you to decide if it's annoying enough to bother.

Open Notepad, or whatever text editor you like, and paste this into it:— #tab-preview-panel {
  display: none !important;
} Save it somewhere easy to find, like the Desktop, and call it userChrome.css (all lower case apart from the C in the middle). Make sure it has saved as userChrome.css and not userChrome.css.txt. In Windows you can right-click it and open Properties to see its full name. Correct it if needed.

In Firefox open about:config and set toolkit.legacyUserProfileCustomizations.stylesheets and browser.tabs.hoverPreview.enabled to true. The latter switches on the new-style hover tabs which can be hidden with the code above.

Now go to about:support. Look down the blue block on the left of the screen that will open until you come to "Profile Directory." Click the "Open Directory" button next to it. This will open your Profile Directory in Windows Explorer, or whatever file browser your system uses.

Make a directory/folder in that called chrome, all lower case. Now drag the userChrome.css file that you created earlier into the new chrome directory.

Restart Firefox for it to take effect.

Thanks, ThePillenwerfer. That's successfully disabled the tab previews when hovering, but not the preview when moving a tab... 🤔

I'd never moved a tab before so didn't know what it did.

Getting rid of its preview is beyond my knowledge so hopefully somebody who knows more than me will be along in due course. If I did have cause to move tabs I'd find it annoying as well.

Is my only option to reinstall an older version of Firefox... again? Firefox 133.0b6 (64-bit)

An older version as in the current Firefox 132.0.1 Release?.

The b6 on Fx 133.0b6 means it is the sixth Beta build of Firefox 133.0 that you are testing. Usually there are nine Beta builds of a version on Beta channel though it used to be as much as fourteen builds.

James, I didn't even know that I was "testing" a beta version! 😮 I just updated to the "latest version" to make the update notification go away!

The latest 'finished' version of Firefox is 132.0.1.