Preheat the oven to 350°F (177°C) and line a 9-cup muffin tin with paper liners.
Place the quick oats in a high-powered blender and blend on low for about 60 seconds, until they form a coarse oat flour.
Add the ground cinnamon, baking powder, and sea salt to the blender and pulse until evenly combined with the oat flour.
In a large bowl, mash the ripe bananas until creamy, then whisk in the eggs, avocado oil, and vanilla extract until smooth.
Pour the blended dry ingredients into the bowl with the wet ingredients and stir until just combined. Fold in the chocolate chips, if using.
Spoon the batter evenly into the prepared muffin tin (about 9 muffins). Top with extra chocolate chips if desired.
Bake on the center rack for 18–22 minutes, or until a digital thermometer inserted into the center of a muffin reads 190°F (88°C) or a toothpick comes out clean.
Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.