Add bacon and kielbasa to a 6 quart Dutch oven then turn the heat to medium. Saute until bacon is golden brown then scoop the meats onto a plate, reserving bacon grease in the pot. Add carrots, celery and shallot then saute until tender, 8-10 minutes - adding a splash of chicken broth then placing a lid on top to speed up softening if it’s taking too long. Add garlic then saute until very fragrant, 1 minute.
Add chicken broth plus 1 cup milk to the pot then turn heat up medium-high to bring soup to a bubble - NOT a boil. Add potatoes then turn heat down to medium and simmer until tender, 5-7 minutes. Meanwhile, whisk together gluten-free flour and remaining 1/2 cup milk until very smooth.
Add browned bacon and kielbasa back into the pot then stream in flour/milk mixture and simmer until soup has slightly thickened, 5 minutes. Add sweet corn then simmer until heated through, 1 minute. Taste then add seasoned salt to taste, and lots of pepper. Scoop into bowls then serve topped with green onions.