I have a 46//30T in the front and an 11-36T in the back. It works fine. By extrapolation, a single chainring ≥ 30T in the front would work fine.

I really appreciate having the 30T in the front and the 36T in the back when I am climbing a 21% grade, or am really tired, or loaded down. I would not be able to ride a 1X like you are considering where I live, even on road.