Heat olive oil in a large saucepan over medium-high. Add onion and cook until soft, about 2 minutes.
Stir in garlic, green onion, celery, bell pepper, cook for another minute, stirring constantly.
Add vegan bouillon, water, dasheen, yuca, kabocha, corn, plantain, crushed tomatoes, oregano, onion powder, and garlic powder to the pot.
Bring sancocho to a boil, then reduce heat to low and simmer until vegetables are tender and soup is thick, for about 30 minutes.
Add cayenne pepper, cilantro, and salt to taste.