Preheat oven to 375°F (190°C).
Line a rimmed baking sheet with parchment paper or foil.
Place oats in a mixing bowl and pour milk over them.
Let the oats hydrate for 5–10 minutes.
Finely dice onion, grate carrot, and mince garlic.
Add egg, Worcestershire sauce, Dijon mustard, thyme, paprika, salt, and pepper to the oat mixture.
Stir in onion, carrot, and garlic.
Add ground beef.
Mix gently just until evenly combined.
Transfer mixture to the prepared baking sheet.
Shape gently into an approximately 9-inch-long loaf.
Mix ketchup, brown sugar, Dijon, apple cider vinegar, and garlic powder in a small bowl.
Spread approximately half the glaze over the raw meatloaf.
Bake uncovered for 30 minutes.
Remove from oven and spread remaining glaze over the top.
Return to oven and bake approximately 20–30 minutes longer.
Check the thickest center with an instant-read thermometer.
Remove when the ground-beef meatloaf reaches 160°F (71°C).
Rest for 10–15 minutes.
Slice and serve.