In a large Dutch oven, cook andouille over medium heat until browned, about 8 minutes. Remove andouille using a slotted spoon, and let drain on paper towels, reserving drippings in pot. Refrigerate andouille until ready to use.
Add onion and bell pepper to drippings; cook, stirring frequently, until onion is translucent, 8 to 10 minutes. Add garlic; cook for 2 minutes. Stir in beans, 4 cups water, parsley, vinegar, bouillon paste, Cajun seasoning, chili powder, hot sauce, oregano, celery seeds, and bay leaf. Bring to a boil; reduce heat, cover, and simmer, stirring occasionally, until beans are tender, about 2 hours. Discard bay leaf.
Using a fork, mash beans to desired consistency. Add andouille, stirring to combine; cook over medium heat until heated through. Serve with rice. Garnish with parsley, if desired.
Recipe by Louisiana Cookin' at https://louisianacookin.com/red-beans-rice/