Not a fan of the new look. If you’re in the same boat, plug:
about:config
into your URL bar, and search for:
browser.nova.enabled
Toggle it to false using the button to the right.
There are functional changes that Nova also introduced: this won’t effect those - only the aesthetic.
Thank you. I’ve read your post yesterday morning and in the afternoon I had to face the change. I came straight back for the fix.