We’ve seen Raspberry Pi cluster boards before, and most of them either use Raspberry Pi Zero boards or Raspberry Pi Compute Modules. Some examples include Turing Pi Clusterboard for up to 7 RPi CM3 modules, Cluster HAT board taking up to 4 Pi Zero board, and Mininodes Raspberry Pi 3 COM Carrier Board.
But some other solutions like Bitscope rely instead on full-sized Raspberry Pi 2/3/4 Model B boards. Another such option is IPTerra CloverPI board allowing up to 4 Raspberry Pi or compatible boards with 40-pin header to be clustered into a single unit powered by one power supply and connected via a 5-port Gigabit Ethernet switch.