Preheat an air fryer to 360 degrees F (180 degrees C).

Combine blueberries, flour, lemon juice, and salt in a small bowl. Toss to coat, then divide the mixture between two 1-cup ramekins.

Combine oats, flour, brown sugar, and cinnamon for the topping in a small bowl. Mix in softened butter using a fork until mixture is crumbly. Sprinkle over the blueberries.

Place the ramekins in the air fryer basket and cook until the blueberries are warmed throughout and topping is golden brown, 12 to 14 minutes.