FWIW the Firefox instructions don't seem to apply to Ubuntu (at least under GNOME, can't speak for any other DE). There's no "three dots," just right click on the address bar, then choose "Add Google Web" from the context menu. Alternatively, you can avoid this nonsense entirely by using DuckDuckGo, or StartPage, or Kagi, or any number of other totally competent search engines.
Same for MacOS