Heat oven to 375°F (190°C). Grease a 24-cup mini muffin tin or line with mini liners.
In a large bowl, whisk flour, baking powder, baking soda, salt, and cinnamon.
In a separate bowl or large measuring cup, whisk Greek yogurt, milk, maple syrup, oil, egg, and vanilla until smooth.
Pour wet into dry and stir with a spatula until just combined. A few small lumps are fine—overmixing = tough muffins.
If using fresh berries, pat dry. Toss with 1 tablespoon flour if you want to prevent sinking (especially with frozen berries).
Gently fold blueberries into the batter. Don't smash them unless you like blue Smurf muffins.
Scoop batter into mini wells, about 3/4 full. Sprinkle with turbinado sugar if using.
Bake 10–12 minutes until tops are set and a toothpick comes out with a few moist crumbs.
Let rest in the pan 5 minutes, then transfer to a rack. Warm muffins are elite; try not to inhale them all at once.