Open 2 cans chickpeas, and drain the liquid (aquafaba) into a large measuring cup (you will get about 2 cups of aquafaba. Set aside ½ cup of the liquid for this recipe (if you want to store the rest of the aquafaba for other recipes, pour it into an airtight jar or container and put it in the fridge). Rinse the chickpeas and drain again.
Heat 2 Tablespoons olive oil in a large pot or dutch oven oven medium heat. Add the minced onion, minced garlic, and ½ teaspoon kosher salt. Cook, stirring often, until the onions are soft, about 5 minutes.
Add 1 teaspoon ground cumin, 1 teaspoon ground coriander, 1 teaspoon smoked paprika, ½ teaspoon freshly ground black pepper, ¼ teaspoon red pepper flakes, and stir. Cook until fragrant, about 30 seconds.
Add the rinsed chickpeas and stir. Lightly mash about half of the chickpeas with a large spoon, fork, or potato masher (this will help to thicken the soup).
Add 4 cups vegetable broth and the reserved 1/2 cup of aquafaba. Increase the heat to medium-high and bring to a boil. Reduce the heat to medium-low, cover loosely with the lid (place the lid on loosely so that it's crooked and slightly open on one side), and simmer for 30 minutes.
Turn off the heat and stir in 5 ounces fresh baby spinach and ½ cup chopped fresh parsley. Once the spinach has wilted, stir in 1 Tablespoon lemon juice. If desired, serve with crusty bread or flatbread.