Rehydrate the soy chunks. Soak them in boiling hot water for 15 to 20 minutes until doubled in size (or in hot water for 20 to 25 minutes if that is the water you have). Squeeze out the excess water once soft.
Marinate. Mix the 1 1/2 tbsp soy sauce and garlic powder into the drained chunks and leave 10 minutes while you prep everything else - this seasons the interior, which the coating will seal in.
Mix the sauce. Combine the sugar, vinegar, pineapple juice, ketchup, 1 tbsp soy sauce, dark soy sauce, 1/4 cup water, 1 1/2 tbsp cornstarch, and pepper in a bowl. Stir until no cornstarch settles at the bottom, then set aside.
Coat. Toss the marinated chunks in the 6 tbsp cornstarch for a heavy first layer, then in the 2 tbsp cornstarch for a thin sealing layer. The double coat is what fries up crisp.
Fry. Heat enough neutral oil to submerge at least half of the chunks over high heat until very hot. Fry until golden and crisp, then drain. Pan-frying instead uses less oil but comes out less crispy.
Build the dish. In 1 to 2 tbsp oil in the same pan over high heat, sauté the onion, garlic, and ginger for 1 to 2 minutes until the onion softens. Add the bell peppers and pineapple chunks and toss briefly.
Sauce and finish. Pour in the sauce, stir until it thickens and turns glossy, then add the fried chunks and toss just to coat. Serve at once over steamed rice - the coating loses crunch quickly once sauced.