Cook the eggs (if needed): Place eggs in a pot, cover with cold water, and bring to a rolling boil. Turn off heat, cover, and let sit 10–12 minutes. Transfer to an ice bath for 5 minutes, then peel.
Prep the mix-ins: Finely chop celery, red onion, and herbs.
Zest about 1/2 teaspoon lemon zest and juice half the lemon to start.
Mash the avocado: In a large bowl, scoop in the avocado and mash with a fork until mostly smooth with a few small chunks. Stir in Greek yogurt, Dijon, lemon juice, lemon zest, garlic powder, salt, and pepper.
Chop the eggs: Dice the peeled eggs into bite-size pieces. If you like a creamier salad, separate the yolks and mash them into the avocado mixture before adding the whites.
Combine: Fold the chopped eggs, celery, red onion, and herbs into the avocado mixture.
Taste and adjust salt, pepper, lemon, and Dijon as needed.
Serve: Spread on toast, spoon into lettuce cups, roll into a wrap, or serve over a bed of greens. Add a sprinkle of dill, chives, or paprika on top.