In a large stock pot or Dutch oven, cook bacon over medium heat until it reaches desired level of crispiness. Using tongs or a slotted spoon, remove the bacon (leave the drippings), set bacon on a plate, and save it for serving.
Add the chopped yellow onion to the pot with the bacon drippings and sauté, stirring frequently, until translucent, about 5 to 8 minutes.
Add the chopped celery root, sweet potato, and apple and continue to cook, stirring occasionally, until vegetables have softened, but are still al dente, about 10 minutes.
Add the beer and 2 cups of the chicken broth. Cover and bring to a full boil.
Reduce the heat to a simmer and continue cooking 5 to 8 minutes, until veggies are cooked through.
Transfer everything from the pot to a blender and blend until smooth.
In a small bowl, whisk together the half and half, flour, shredded cheddar cheese, and remaining 1 cup of chicken broth until all the flour clumps are out.
Add the half and half mixture into the empty pot and heat over medium, stirring until the cheese has melted and the mixture has thickened, about 3 minutes.
Add the blended soup back into the pot with the cheesy mixture and stir to combine. Serve soup hot with a dollop of greek yogurt or sour cream, chopped red onion, and crumbled bacon.