  Random flux is commonly believed to be incapable of driving full
metal-insulator transitions in non-interacting systems. Here we show that
random flux can after all induce a full metal-band insulator transition in the
two-dimensional Su-Schrieffer-Heeger model. Remarkably, we find that the
resulting insulator can be an extrinsic higher-order topological insulator with
zero-energy corner modes in proper regimes, rather than a conventional Anderson
insulator. Employing both level statistics and finite-size scaling analysis, we
characterize the metal-band insulator transition and numerically extract its
critical exponent as $\nu=2.48\pm0.08$. To reveal the physical mechanism
underlying the transition, we present an effective band structure picture based
on the random flux averaged Green's function.
