Combine chopped fresh strawberries, 2 tbsp granulated sugar, and 1 tsp lemon juice in a small saucepan over medium heat. Cook for 8–10 minutes, stirring occasionally, until the mixture breaks down and turns jammy.

Remove the strawberry mixture from the heat and mash slightly. Let it cool completely before using.

Combine fresh blueberries, 2 tbsp granulated sugar, and 1 tsp lemon juice in a small saucepan over medium heat. Cook for 8–10 minutes, stirring occasionally, until thick and deeply colored.

Remove the blueberry mixture from the heat and mash slightly. Let it cool completely before using.

In a large chilled bowl, beat cold heavy whipping cream with a hand mixer on high until stiff peaks form, about 3–4 minutes. Do not over-whip.

Gently fold the sweetened condensed milk, pure vanilla extract, and a pinch of salt into the whipped cream until fully combined. Mix just until fluffy and not deflated.

Pour half the ice cream base into a 9x5 loaf pan. Drop spoonfuls of the strawberry swirl and blueberry swirl over the base layer, using about half of each.

Layer the remaining ice cream base on top of the swirls. Add the remaining strawberry swirl and blueberry swirl on top.

Run a knife or skewer through the pan in wide S-shaped strokes, 3–4 passes only. Stop after 3–4 passes to keep bold, defined red, white, and blue ribbons.

Cover tightly with plastic wrap, pressing it directly onto the surface. Freeze for at least 6 hours, preferably overnight, until completely set.

Remove the ice cream from the freezer 5 minutes before scooping. Scoop into bowls or cones and top with sliced fresh strawberries, fresh blueberries, and white sprinkles or star-shaped confetti sprinkles before serving immediately.