Preheat the oven to 350 degrees F (175 degrees C). Line a 12-cup muffin tin with paper liners.
Whisk almond milk, mashed banana, and vanilla extract together in a large mixing bowl until smooth. Add oats, brown sugar, cinnamon, baking powder, and sea salt; mix until well combined. Fold in blueberries. Fill the prepared muffin cups evenly with batter.
Bake in the preheated oven until tops spring back when lightly pressed, about 25 minutes. Cool in the tin for 5 minutes. Transfer to a wire rack to cool completely.