Prep the tuna: Drain the cans well and flake the tuna with a fork in a large mixing bowl to break up any big chunks.
Make the dressing: In a small bowl, whisk together Greek yogurt, mayonnaise, olive oil, lemon juice, and Dijon. Add garlic powder, a pinch of salt, and pepper.
Add the crunch: Stir in celery, red onion, pickles, and herbs.
Mix until evenly combined.
Combine: Add the dressing to the tuna and fold gently until everything is coated. Taste and adjust salt, pepper, or lemon juice.
Optional boosts: Fold in chickpeas, diced avocado, or chopped hard-boiled egg if using. Keep the avocado for serving time if prepping ahead.
Serve: Spoon into lettuce leaves, layer on toast, tuck into a wrap, or pile onto your favorite crackers.