Preheat a smoker to 250°F. Combine the Greek yogurt, squeezed cucumber, lemon juice, dill, and olive oil in a small bowl. Stir until smooth, cover, and refrigerate while you prepare the meatloaf.
In a large bowl, gently mix the ground beef, egg, almond flour, feta, olives, red onion, garlic, oregano, salt, and pepper. Stop mixing as soon as the ingredients are evenly distributed to help keep the meatloaf tender.
Shape the mixture into a compact loaf about 7 inches long. Set it on a smoker-safe tray or directly on a clean smoker rack.
Smoke until the center reaches 160°F on an instant-read thermometer, checking the temperature in the thickest part of the loaf.
Rest the meatloaf for 10 minutes before slicing. Serve warm with the chilled tzatziki.