Preheat oven to 350°F (175°C). Grease a 9x5-inch loaf pan.
In a large bowl, whisk together bananas, eggs, applesauce, Greek yogurt, sweetener, and vanilla.
In another bowl, mix flour, baking soda, cinnamon, and salt.
Combine wet and dry ingredients until just mixed. Fold in walnuts or chocolate if using.
Pour batter into the loaf pan and bake for 45–50 minutes, or until a toothpick inserted in the center comes out clean.
Cool before slicing. Store leftovers in the fridge.