Rinse the brown lentils thoroughly. In a medium saucepan, combine the rinsed lentils with vegetable broth. Bring to a boil, then reduce heat, cover, and simmer for 20-25 minutes, or until tender. Drain any excess liquid and set aside.

While lentils cook, heat olive oil in a large skillet or Dutch oven over medium heat. Add the chopped onion and bell pepper, and sauté until softened, about 5-7 minutes.

Add the finely chopped mushrooms and minced garlic to the skillet. Cook, stirring occasionally, until the mushrooms have released their liquid and are browned, about 8-10 minutes.

Stir in the tomato paste and cook for 1 minute until fragrant. Then, add the ketchup, vegan Worcestershire sauce, maple syrup, smoked paprika, chili powder, and Dijon mustard. Stir to combine.

Add the cooked lentils to the skillet with the vegetable mixture. Stir well to ensure everything is coated. Season with salt and black pepper to taste.

Reduce the heat to low, cover the skillet, and let the mixture simmer for at least 10-15 minutes to allow the flavors to meld. Stir in the apple cider vinegar just before serving.