tldr; Firefox changed the order in which suggestions appear when you start typing in the address bar. It used to show previously visited websites first. Now it prioritizes its own suggestions.
To get back to the old behaviour, navigate to about:config, search for the key browser.urlbar.showSearchSuggestionsFirst and change the value to false.
The article talks about search suggestions. Those are from the search provider, not Firefox.
I’ve always had them disabled. It’s not like I need suggestions of what to search for or what I may want to search for.
There are search suggestions and there are also Firefox suggestions. You can see them both in the settings separately.