Cut the turkey bacon into small pieces using kitchen shears for ease. Add it to a soup pot and cook over medium-high heat until crispy, about 10 minutes.
While the bacon cooks, prepare the onion and potatoes. You may peel the potatoes or leave the skin on if you prefer.
Once the turkey bacon is crisp, remove it from the pot and place it on a paper towel-lined plate to drain. Leave approximately two tablespoons of the fat in the pot, discarding or reserving the rest.
Add the chopped onion to the pot and sauté for 5 minutes.
Stir in the flour and cook for about one minute.
Slowly whisk in the milk until the flour is fully dissolved.
Add the chicken broth, minced garlic, and diced potatoes. Raise the heat to high, scraping up any browned bits from the bottom of the pot.
Once the soup begins to boil, reduce the heat to low and cover with the lid slightly ajar. Let it simmer gently for 20 minutes.
While the soup cooks, prepare the cheddar cheese, scallions, and sour cream.
When the potatoes are very tender and starting to fall apart, mash them slightly in the pot if you like, or leave them whole.
Stir in the sour cream, most of the cheddar cheese, and the cooked turkey bacon, reserving some for topping. Season with salt and pepper to taste.
Ladle the soup into bowls and garnish each with the remaining scallions, cheddar, and turkey bacon.