R86 stepper motor driver. No earth

[Muzzer]

Not really sure what the issue was here. The driver is clearly supposed to be supplied by an isolated AC (from transformer) or DC (from a PSU). The motor phase connections and that the output of the AC or DC supply will be floating with respect to ground, so you don't NEED to ground any of it. You CAN ground that circuit if you wish - for instance you might choose to ground the DC- side of the PSU is you went the PSU route. The output (motor phase) connections are not isolated from the AC/DC input to the driver and typical low voltage stepper motors are not designed and constructed to be connected to live mains, so electrical isolation between the mains and the drive voltage is required - this is provided by the transformer / PSU.

This is normal practice for these low voltage drivers, so there's no obvious need for any information beyond what they've provided. It's really no different from any other low voltage stepper driver other than the fact it will accept either AC or DC on the input.