Heat oil in a large, heavy-bottomed, non-reactive Dutch oven over medium heat until shimmering but not smoking, 3-4 minutes.
Add bacon and brown for 5-6 minutes or until golden brown and crisp. Remove and set aside on a plate.
In the same pot, add onions and garlic and saute until onions soften.
Add the diced smoked brisket along with cumin, oregano, coriander, cayenne pepper, and dried thyme. Cook for 4-5 minutes.
Pour in diced tomatoes and tomato sauce, add drained beans, bell pepper, jalapenos, chili powder, beef stock, and water (about ½ cup or more), and lightly salt and pepper.
Bring to a boil, then reduce heat to low and simmer for an hour or so, stirring occasionally (if chili begins to stick to the bottom of pot, stir in ½ cup of water and continue simmering), until brisket is tender and chili is dark, rich, and slightly thickened.
Adjust seasoning with additional salt, pepper, and liquid as needed.
Serve hot with shredded cheddar and chopped green onions as garnish or any desired toppings. Enjoy!