Preheat oven to 350 degrees F (175 degrees C). Grease 24 muffin cups or line with paper muffin liners.
Whisk together flour, oats, flax, sugar, coconut, cinnamon, baking powder, baking soda, and salt in a bowl.
Whisk together bananas, sour cream, applesauce, melted butter, eggs, and vanilla in a large bowl. Stir flour mixture into banana mixture just until all dry ingredients are moistened; fold in blueberries. Fill muffin cups 2/3 full.
Bake in the preheated oven until a toothpick inserted near the center comes out clean, about 20 minutes.