Bring a large pot of salted water to a boil; add noodles, cover the pot with a lid, and cook for 7-9 minutes or until pasta is al dente.
Stir soy sauce, oyster sauce, brown sugar, sesame oil, cornstarch, ginger, garlic, and Sriracha sauce, together in a small bowl.
Heat avocado oil in a large skillet; sauté steak in oil until browned completely, 2 to 3 minutes.
Pour sauce over the beef; stir coating beef well. Add noodles; cook on low heat until warmed through, stirring continously, so sauce coats the noodles, 1 to 2 minutes.
Sprinkle most of the green onions and sesame seeds over the lo mein; stir to incorporate.
Divide into bowls; garnish with more green onion and sesame seeds to serve.