Are people still making this brownie?

I agree with Lori, but would add that the baking powder is essential to give this cake some lift. Without it - especially as no eggs are used - this fudgy vegan banana brownie cake will be flat and hard, like a giant hockey puck. ;o)

Oat flour is considered a viable substitute for almond flour, so I don't see a problem with doing that if you so desire. But if you leave out the maple syrup, I don't believe you will enjoy the taste. You'd still want to add a sweetener of some sort, your choice, but try to use on formulated for baking. And you do really need the lift of that little bit of baking powder. Frankly, you can't make a really good brownie with "no" ingredients. Ain't happening. While it's possible to make a brownie with fewer "bad" ingredients, or at least smaller measures of them, you just have to make a few concessions. Cocoa with no sweetener doesn't taste good, or all the chocoholics in the world would be eating the stuff by the spoonful from the container, and staying skinny. My suggestion would be to consider a sweetener substitute designed for baking, use the oat flour if you wish, and keep everything else as is. You want a good brownie, you just have to use the stuff that makes one.