No idea if there's a hard ban, but I was there 2 years ago and did not notice extensive smoking in restaurants. There may have been none, or someone doing it far from me, but I didn't have any meal impacted by secondhand smoke. I too am a nonsmoker and would notice it quick if somebody near me was smoking.

I did not experience Dubai's bar/club scene except for my hotel's bar, where nobody smoked.

I know smoking is still part of the culture in some parts of the Middle East, but I would think that nonsmokers could have an enjoyable time in Dubai without inescapable smoke.

Egypt, as an example, was a lot "smokier" when I was there 10 years ago. More of it in my hotel as well as pretty much every cafe.