In a large pot, bring 4 quarts salted water to a boil. Add cabbage, carrots, and celery and cook until slightly softened, about 2 minutes. Transfer to an ice bath.

Once cool enough to handle, drain and squeeze veggies with a kitchen towel until water is removed; set aside.

In a small bowl, combine soy sauce, hoisin, oyster sauce, and sesame oil.

In a large skillet over medium-high heat, heat vegetable oil until shimmering. Cook garlic and ginger, stirring, until fragrant, about 30 seconds. Add pork and cook, breaking up with a spoon, until browned and starting to crisp, 4 to 5 minutes.

Drain fat from skillet until about 1 tablespoon remains. Add soy sauce mixture and toss pork to coat. Cook over medium-high heat, stirring, 1 minute. Add veggies and cook, stirring, until combined and warmed through, 2 to 3 minutes more; season with salt and black pepper. Let cool slightly.

On a clean work surface, arrange an egg roll wrapper in a diamond shape. Spoon 2 heaping tablespoons filling onto bottom third of wrapper. Fold up bottom half and tightly fold in sides. Gently roll and seal edges with a couple drops of water, pressing to adhere.

Working in batches, generously brush egg rolls with vegetable oil. In an air- fryer basket, arrange egg rolls in a single layer. Cook at 400°, flipping halfway through, until golden brown and crispy, about 10 minutes.

Serve egg rolls with mustard and duck sauce alongside.