From my understanding, if you use DEP the device should become supervised by any means, even if an unsupervised backup is applied. Is your Meraki Management Profile locked on the device - if so, the device is supervised?
I had a user who had an unsupervised backup on iTunes on their computer. I went through setup, signing in with his AD creds to start enrollment and then plugged into iTunes and restored, seems to be working for us.
Jared
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