Preheat oven to 350°F (175°C). Line a 12-cup muffin pan with liners or spray with non-stick spray.
In a high-speed blender, add almond milk, egg, Greek yogurt, oats, sugar substitute, whey protein powder, baking powder, baking soda, cinnamon, salt, and vanilla extract (liquids first).
Blend on medium-high for 30-45 seconds until smooth. Scrape down sides if needed.
In a small bowl, toss blueberries with ½ tbsp oat flour to coat.
Pour batter evenly into muffin cups (almost full). Drop blueberries on top, pressing them gently into the batter.
Bake at 350°F for 20-25 minutes until a toothpick comes out clean.
Cool in pan for 5 minutes, then transfer to a wire rack to cool completely.