Add oil and bacon pieces to a large skillet over medium heat. Cook for 7-8 minutes. Remove and allow to drain on a paper towel-lined plate. Reserve bacon grease in skillet.
Add diced onion and minced garlic to the skillet, cook for 2-3 minutes.Now add cut greens. Pour in chicken broth and add salt, pepper, and red pepper flakes. Stir until well-combined.
Cover the skillet with a lid and cook for 34-40 minutes. Stir every 10 minutes. Turn off heat and mix in cooked bacon and vinegar. Serve immediately, and enjoy!