Heat oil in a large non-stick skillet on medium-high heat.
Arrange the diced potatoes in a single layer and cook without moving for about 2 minutes until the bottom is slightly browned. Give them a quick stir and let them brown again for 2 more minutes.
Push the potatoes to one side of the skillet and add the ground beef to the other side. Season both with salt and pepper.
Break the ground beef apart with a wooden spoon and spread it out to cover its half of the pan. Press it down and cook undisturbed for 4 minutes, stirring the potatoes occasionally.
Scoop out any extra grease from the beef if you like.
Add the chopped onion, bell pepper, minced garlic, and smoked paprika over the beef and potatoes. Stir everything together until well mixed.
Continue cooking while stirring now and then until the veggies soften, the beef turns fully brown, and the potatoes can be easily pierced with a fork, about 3 to 4 minutes.
Turn off the stove, sprinkle shredded Cheddar on top, and let the heat melt the cheese.
Finish by adding the chopped green onions over the skillet and serve hot.