Place rinsed chickpeas in a large bowl. Mash with a fork until some are completely smooth but most remain chunky. Add flaked drained tuna; stir to combine.
Add ½ cup yogurt, 5 tablespoons mayonnaise, the sliced celery, ⅓ cup scallions, ¼ cup capers, 2½ tablespoons lemon juice, 2 tablespoons everything bagel seasoning, ½ teaspoon pepper and ¼ teaspoon plus ⅛ teaspoon salt; mix until evenly combined.
Divide the salad evenly among 16 lettuce leaves (about ¼ cup each), using about 3 to 4 leaves per serving.
