Good NP-complete reduction candidates for disjoint bilinear programs

Given a disjoint bilinear programm $ max\{x^TQy: x \in X, y\in Y\}$ , with $ Q$ being a matrix and $ X$ and $ Y$ specific polytops (i.e. like X = knapsack polytop or Y = stable set polytop)

What are some good NP-complete problems, which look similiar and are known to be np-complete. Classic problem like knapsack, stable set are difficult because they do not have this disjoint product property?

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