Piecewise-smooth systems are common in applications, ranging from dry friction oscillators in mechanics, to power converters in electrical engineering, to neuron cells in biology. While the properties of stability and the control of such dynamical systems have been studied extensively, the conditions that trigger specific collective dynamics when many of such systems are interconnected in a network are not fully understood. The study of emergent behaviour, and in particular synchronization, has applicability in seismology, for what concerns the dynamics of neighbouring faults, in determining load balancing in power grids, and more. To enforce asymptotic state synchronization, we propose the addition of a discontinuous coupling action to the commonly used diffusive coupling term; even with the possibility that the two coupling protocols are associated to different graph topologies. This allows that convergence is achieved regardless of initial conditions, and without the use of any centralised control action. Moreover, we show that the minimum threshold on the coupling gain associated to the new discontinuous coupling protocol depends on the density of the sparsest cut in the graph. Namely, this crucial quantity, which we called minimum density, plays a role very similar to that of the algebraic connectivity in the case of networks of smooth systems, in describing the relation between synchronizability and topology.