Prep the eggs: Roughly chop the hard-boiled eggs. Aim for a mix of small and medium pieces so the salad has some texture.
Mash the avocado: In a large bowl, add the avocado and lemon juice. Mash with a fork until mostly smooth with some small chunks left.
The citrus helps prevent browning and brightens the flavor.
Add flavor: Stir in the Dijon, red onion, dill, celery, and garlic (if using). If you like more creaminess, add the Greek yogurt now.
Combine: Gently fold in the chopped eggs. You want to coat the eggs well without smashing them completely.
Season: Add salt, black pepper, and red pepper flakes or hot sauce if you like a little heat.
Taste and adjust lemon, salt, and mustard as needed.
Serve: Spoon onto toasted sourdough, whole-grain bread, or into lettuce cups. You can also serve it as a dip with cucumbers and crackers.