We have handled some support cases about the issue which happens before the Work managed device provisioning. Some Samsung devices states the error "The security policy prevents the creation of a managed device because a custom OS is or has been installed on this device" when trying to e.g.read the QR code. We assume the reason for this issue is the wrong time setting in the device. To fix this, you will need update the time on the device by either connecting to wifi or cellular data (insert SIM-card), or by manually changing it in the set-up screen. After this is done you will be able to provision the device. Usually that should help.
UPDATE: Please see Samsung's document about that error here:
- Jarkko / Miradore Online Support