Heat a smoker to 250°F. Line a small rimmed baking sheet with foil for the plantains.
In a large bowl, combine the ground beef, egg, breadcrumbs, onion, tomato paste, cocoa powder, ancho chile powder, cinnamon, cumin, chipotle powder, salt, and black pepper. Mix gently until evenly combined, taking care not to pack the meat too tightly.
Shape the mixture into a compact loaf and place it on a smoker-safe rack or a foil-lined pan. Set it in the smoker and cook until the center reaches 160°F, checking with an instant-read thermometer.
While the meatloaf smokes, toss the plantain slices with the olive oil. Arrange them in a single layer on the prepared baking sheet.
When the meatloaf is nearly done, roast the plantains in a 425°F oven for about 20 minutes, turning them once, until tender and browned at the edges.
Remove the meatloaf from the smoker and let it rest for 10 minutes before slicing. Sprinkle the roasted plantains with the chopped cilantro and serve them alongside the meatloaf.