Preheat the oven to 350°F and line a 9x5-inch loaf pan with parchment paper, leaving overhang for easy removal.
In a medium bowl, whisk together the gluten-free flour, cocoa powder, baking soda, and salt. Set aside.
In a large bowl, mash the bananas until smooth and creamy. Add maple syrup, granulated sugar (if using), and oil, mixing until well combined.
Whisk in the eggs and vanilla extract until smooth.
Gradually add half of the dry ingredients to the banana mixture, stirring gently with a spatula. Add non-dairy milk, then the rest of the dry ingredients, mixing just until combined.
Fold in chocolate chips, reserving some for the top.
Pour batter into the prepared loaf pan, smooth the top, and sprinkle reserved chocolate chips on top. Bake for 45-55 minutes, covering with foil at 30 minutes to prevent excessive browning. Check for doneness with a toothpick – it should come out with a few moist crumbs.
Cool in the pan for 10 minutes, then lift the bread out using the parchment overhang. Cool completely on a wire rack before slicing.