Musakhan (Palestinian Chicken and Potatoes)

Name: Musakhan (Palestinian Chicken and Potatoes)
Prep time: 5 min
Cook time: 55 min
Total time: 1 h
Cuisine: Middle Eastern
Ingredients: 4 chicken legs, split into drumsticks and thighs (about 3 pounds; 1.3 kg total); 2 pounds (907 g) small yellow medium-starch potatoes such as Yukon Gold, peeled, halved lengthwise, and cut crosswise into 1/2-inch slices; 6 tablespoons (90 ml) extra-virgin olive oil; 2 tablespoons sumac, plus more for serving (see notes); 2 1/4 teaspoons ground allspice; 2 teaspoons ground coriander; 1 1/2 teaspoons ground cinnamon; 1 teaspoon ground ginger; 1 teaspoon ground cardamom; 1 teaspoon freshly ground black pepper; 4 teaspoons (12 g) Diamond Crystal kosher salt, for table salt, use half as much by volume or the same. weight; 2 medium yellow onions (about 16 ounces total), cut into 1/2-inch slices; 1/4 cup (6 g) finely chopped fresh oregano leaves, plus more for serving; Lemon wedges, for serving; Plain whole-milk yogurt, for serving