For the spicy ketchup sauce: Add the ketchup, vinegar and hot chili sauce to a bowl and stir. Reserve 1/2 cup for the meatloaf.
For the meatloaf: In a large bowl, whisk together the Worcestershire sauce, egg, salt, pepper, paprika, garlic, thyme, onions, scallions and reserved spicy ketchup sauce. Crumble half the chuck into the bowl, followed by some bread, then half the turkey pile on some more bread cubes. Repeat with the other half of meat and remaining bread. (So a half pound of crumbled chuck, some bread, then a half pound of ground turkey, some bread and repeat until done. Adding this way will make mixing easier and lighter for a juicier loaf.) Gently mix with 1 hand, bringing the egg mixture from the bottom to the top and around until everything is gently combined. Place into a 9 by 5-inch loaf pan, flatten the top and pour the remaining spicy ketchup sauce over the top evenly. Bake in the oven for 60 minutes. Remove and allow to rest for 10 minutes.
Tilt the loaf pan slowly to 1 corner and discard any excess fat or juices from the pan while holding the loaf inside. Don't worry, the meatloaf will still be juicy! Slice into 1-inch thick portions. Serve warm and if there's anything left, refrigerate it and enjoy a meatloaf sandwich for leftovers the next day.