Melt butter in pot over medium heat.
Add onions, celery, and mushrooms. Cook for 5-6 minutes until soft, stirring occasionally to avoid burning.
Add garlic. Stir for 1 more minute.
Sprinkle flour over vegetables and mix. Continue stirring for 2-3 minutes until flour is dissolved.
Add tomatoes. If using whole tomatoes, use spatula or clean hands to break into pieces.
Add potatoes, chickpeas with liquid, water, thyme, sea salt, black pepper, cayenne, kelp, Old Bay, and sriracha. Stir to combine.
Bring to boil, then cover and turn to low.
Cook for about 20 minutes until potatoes are soft. Open pot to stir every 3-4 minutes to avoid burning.
Add greens and take off heat. Cover for 2 minutes to allow greens to wilt.
Add plant milk. Stir. Cover and let sit for at least 10 minutes to allow flavors to blend and broth to thicken.
Taste soup. Adjust seasonings as needed (salt, pepper, sriracha).
Ladle and serve with fresh cracked pepper, fresh parsley or fresh bread.