In a large bowl, whisk vinegar, 2 tablespoons soy sauce, 1 tablespoon cornstarch, 1 tablespoon garlic, and 1 tablespoon ginger until cornstarch is dissolved. Add steak and toss to coat. Let marinate at room temperature 15 to 30 minutes.

Meanwhile, bring a medium pot of water to a boil over high heat. Add contents of 1 ramen seasoning packet and stir to combine. Add all ramen noodles and cook, stirring occasionally, until just tender, about 2 minutes. Break up any clumps of noodles still intact with a fork, then drain.

In a small bowl, whisk remaining 4 tablespoons soy sauce and 1 tablespoon cornstarch until dissolved. Add oyster sauce, sugar, second ramen seasoning packet, and ¾ cup water and whisk to combine.

In a large skillet over medium-high heat, heat 1 tablespoon oil. When oil is shimmering, add half of beef. Spread into an even layer and cook, undisturbed, until browned on the bottom, 2 to 3 minutes. Stir to redistribute beef and continue to cook, stirring often, until just cooked through, about 30 seconds more. Transfer to a plate. Repeat with 1 tablespoon oil and remaining beef.

In same skillet over medium-high heat, heat 2 tablespoons oil. Add broccoli and cook, stirring often, until bright green, 1 to 2 minutes.

Push broccoli to one side of skillet. Add remaining 1 tablespoon oil, 1 tablespoon garlic, and 1 tablespoon ginger to empty side of pan. Cook, stirring, until fragrant, 30 seconds to 1 minute, then toss to combine with broccoli.

Briefly mix sauce to combine and pour over broccoli mixture. Cover and cook until broccoli is just tender, 2 to 4 minutes.

Uncover, add reserved ramen noodles, beef, and any accumulated juices, and toss to combine. Cook, tossing, until coated and glossy, about 30 seconds more. Top with sesame seeds.