I'm a huge fan of the navigation bar on the bottom. I've missed it since I had to give up Windows Phone. It's hard to believe that neither Apple or Google ever added the option. I can't think of a single reason it would be better on top, It's simply harder to reach and less usable.
Brave on Android has had bottom-bar for quite a while, it was the reason I switched from Firefox. I would switch back, but as there is no add-on support...
This also goes for all other apps...