Heat a smoker to 250°F. In a large bowl, combine the ground beef, breadcrumbs, egg, onion, milk, salt, and black pepper. Mix gently until just combined.

Divide the mixture into four equal portions and shape each into a small loaf. Wrap two slices of bacon around each loaf, tucking the ends underneath so they stay in place.

In a small bowl, stir together the bourbon, ketchup, brown sugar, and Dijon mustard. Set aside half of the mixture for serving, and use the rest to brush the bacon-wrapped loaves.

Put the Brussels sprouts in a bowl and toss them with the olive oil and garlic powder. Spread them in a single layer in a shallow roasting pan or on a rimmed pan that fits in the smoker.

Arrange the meatloaves on a rack above the pan of Brussels sprouts, or place them beside the sprouts if your smoker has room. Smoke until the meatloaves reach an internal temperature of 160°F and the sprouts are tender with browned edges, about 1 to 1 1/2 hours. Brush the loaves once more with the glaze during the final 20 minutes.

Transfer the meatloaves and sprouts to a serving platter. Let the loaves rest for 5 minutes, then serve with the reserved bourbon glaze.