Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan.

In a medium mixing bowl, whisk together the flour, baking soda, salt, and ground cinnamon.

In a large mixing bowl, cream together the softened butter and granulated sugar for 2-3 minutes until light and fluffy.

Add in the eggs one at a time, beating well after each addition until smooth.

Mash the ripe bananas, then add them along with Greek yogurt and vanilla extract to the mixture and combine well.

Gradually stir the dry ingredients into the wet ingredients until just combined.

Fold in the fresh blueberries gently to avoid breaking them.

In a small bowl, mix together granulated sugar and ground cinnamon for the swirl filler.

Pour half of the batter into the loaf pan, sprinkle with half of the cinnamon-sugar mixture, and add the remaining batter on top, finishing with the rest of the cinnamon-sugar mixture.

Gently swirl the batter with a knife to create marbled patterns without overmixing.

Bake for 50-60 minutes, checking for doneness at 50 minutes.

Let the bread cool in the pan for 10 minutes before transferring to a wire rack to cool completely.