Tbh any turbine likely has the potential to be blocked, if two come along at once, making one become trapped between the turbine blade and the wall.

For maximal efficiency, I would suggest a spring-loaded ring of rollers inside a solid metal ring, conforming to the shape of passing Linux users. The dynamos would need to be calibrated such that the stiction of passing users is enough to slow their fall to match the current flow rate of entering users (n.b. is this doable? If not may need to use the spring pressure for this) to ensure maximal energy extraction for available user flow.