Dedoimedo shows you how to change the new address bar in Firefox 75 and higher.

How to change the address bar in Firefox 75 (and beyond)

Behold, an important tutorial showing how to change the new Firefox address bar (urlbar) with its zoom-like functionality to classic look & feel, covering both Firefox 75 and Firefox 77 nightly builds, including manual creation of userChrome.css file in the Firefox profile, use of custom styles to override the address bar look, a few other tweaks, and more. Enjoy. I know I did.

How to change the address bar in Firefox 75 (and beyond)