Construct quantum constraints for arbitrary rank
Construct, for general rank $M\geq 2$, a complete system of q-difference operators annihilating the rank-$M$ partition function $Z_{U(M)}[y_1,\ldots,y_M]$ whose classical limit defines the corresponding Lagrangian variety in $(\mathbb{C}^*)^{2M}$, and solve this system.
References
Unfortunately we do not know how to solve this problem for the general rank $M$.
At present, however, we do not know how to derive the remaining independent quantum constraints.
In general, it is not known whether superintegrability persists, and the $q$-Virasoro constraints need not provide a well-defined recursive prescription for determining all correlators. Consequently, for a generic $q$-deformed matrix model we do not know how to construct systematically an operator $\hat{A}{U(1)}$ annihilating $Z{U(1)}[y]$.