Mango and Halloumi Fritto Misto

Name: Mango-and-Halloumi Fritto Misto
Ingredients: Neutral oil (such as grapeseed), for frying; 2 cups all-purpose flour (about 8 1/2 ounces); 1/2 cup cornstarch (about 2 1/4 ounces); 1 teaspoon baking powder; 2 teaspoons kosher salt, divided; 2 1/2 cups club soda; 2 ripe-but-firm medium mangoes, peeled and cut into 3/4-inch wedges; 8 ounces halloumi cheese, cut into 1-inch pieces; 6 medium scallions, cut into 4-inch pieces; 1 medium lemon, thinly sliced and seeded; Chile oil, for serving