Parboil diced potatoes in salted water until just tender, 5–7 minutes. Drain very well.
Heat a large skillet over medium-high. Melt butter with olive oil.
Soften onion and bell pepper in the fat, stirring, about 3–4 minutes.
Stir in garlic and thyme. Cook until fragrant, about 30 seconds.
Add drained potatoes. Spread in an even layer and cook undisturbed to brown, 5–7 minutes.
Fold in corned beef and beets. Season with salt, pepper, and paprika.
Splash in vinegar and Worcestershire. Press the hash down and cook until crisp, 6–8 minutes, flipping in big sections.
Finish with parsley. Taste and adjust seasoning. Serve hot.