Stir the milk, vinegar, and butter together in a large mixing bowl and let sit for 5 minutes.
Stir the flour, baking powder, baking soda, and salt in with the milk until thoroughly combined.
Drop 8 mounds (about 1/3-cup in size each) of the mixture onto a baking sheet at least 2-inches apart from one another.
Place in the preheated oven and bake until lightly browned, about 20 minutes. Start the sausage gravy while the biscuits are in the oven.
GRAVY:
Add the pork to a dutch oven over medium-high heat. Cook the pork until browned, breaking up the pork with a wooden spoon or spatula while it cooks, about 7 minutes.
Add the butter, sage, garlic, crushed red pepper, 1/2 tsp salt, and 1/4 tsp pepper and stir until well combined and butter has melted.
Add the flour and stir until thoroughly combined. Slowly pour in the milk as you stir and coook, stirring often, until it just begins to boil.
Reduce heat to low and simmer, stirring occasionally while scraping the bottom of the pan with a wooden spoon, until thickened, about 10 minutes. Season with salt & pepper to taste.