Gently toss one 7⅓-oz. bag plain pita chips with 2 Tbsp. extra-virgin olive oil in a large bowl until well coated. Add 1 Tbsp. sumac, and 2 tsp. granulated sugar and toss to coat; set aside.

Toss zest of 1 large lemon, 3 garlic cloves, finely grated, 2 cups cherry tomatoes (about 10 oz.), halved, ½ cup fresh lemon juice, 1 Tbsp. sumac, and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt in a large bowl to combine; set aside.

Rub 1 lb. boneless New York strip steak with 1 Tbsp. extra-virgin olive oil. Season generously with salt and freshly ground black pepper. Rub 3 ears of corn, husked, with 1 Tbsp. extra-virgin olive oil.

Prepare a grill for medium-high heat; oil grate. Grill steak, corn, and 1 bunch scallions (arrange scallions perpendicular across grate so they don’t fall through), turning occasionally, until steak is charred and an instant-read thermometer inserted into the thickest part registers 120°, 6–8 minutes for medium-rare; scallions are charred and softened, 6–8 minutes; and corn is blistered and tender, 8–10 minutes. Transfer each to a cutting board as ready and let rest 10 minutes.

Trim roots from scallion and discard. Cut into ½"-long pieces. Cut corn kernels from cobs; discard cobs. Transfer scallions and corn kernels to bowl with reserved tomato mixture and add 4 Persian cucumbers, halved lengthwise, sliced crosswise on a diagonal ½" thick, 1 bunch red radishes, trimmed, thinly sliced, 2 cups (loosely packed) coarsely chopped mixed tender herbs (such as parsley, dill, and/or mint), 6 Tbsp. extra-virgin olive oil, and reserved seasoned pita chips. Toss gently to combine; taste salad and season with more salt and pepper if needed.

Pile salad onto a platter. Thinly slice steak against the grain into ¼"-thick strips and arrange over salad; drizzle with more oil.