Wash and peel the cucumbers, then chop them into chunks.
Cut the avocados in half, remove the pit, and scoop the flesh into a blender or food processor.
Add the chopped cucumbers, vegetable broth, Greek yogurt, lime juice, minced garlic, salt, and pepper into the blender with the avocado.
Blend the mixture on high speed until smooth and creamy. Adjust the consistency by adding more vegetable broth if too thick.
Taste and adjust the seasoning as necessary.
Transfer the soup to a mixing bowl, cover, and chill in the refrigerator for at least 30 minutes before serving.
Serve the soup cold in individual bowls, garnished with fresh dill or mint.