Place the eggs in a small saucepan and cover with water; bring to a boil, then cover, remove from heat, and let sit for 10 minutes before cooling in ice water.
Drain the canned tuna thoroughly using a fine-mesh sieve to remove all excess liquid before placing it in a medium mixing bowl.
In a separate small bowl, whisk together the avocado oil mayonnaise, Dijon mustard, lemon juice, sea salt, black pepper, and dried dill until smooth and creamy.
Pour the dressing over the tuna and fold gently with a spatula until the fish is well-coated and the mixture is uniform.
Arrange the mixed baby greens in a wide serving bowl and top with the prepared tuna salad, diced cucumber, and crumbled feta cheese.
Peel the hard-boiled eggs, slice them in half, and nestle them into the bowl for a complete, high-protein meal.