The current answer to the question Highest number of satellites launched on a single rocket is 104, on ISRO's PSLV-C37. One of the runner-ups is KANOPUS-V-IK with about 73 satellites. The trick is to land an order from Planet Laps for a flock of doves. The Doves should be considered mostly identical here, and would count as one satellite design.
edit: So far there are no answers, so I'll make another adjustment. The whole concept of the cubesat standard is that they should all deploy the same. A cubesat "dispenser" should not care who's cube it is or how it was designed internally. Therefore:
1U, 2U, 3U, 6U, etc. Each cubesat size counts as one design for the purposes of this question. I'm trying to get a handle on the variety of satellite shapes and sizes that a single rocket must handle.
below: Cropped from Spaceflight Now's Soyuz rolled out for launch of multinational satellite cluster Some of the 73 satellites slated to launch on a Russian Soyuz rocket Friday are pictured before encapsulation inside the launcher’s payload fairing at the Baikonur Cosmodrome in Kazakhstan. Credit: Glavkosmos