i just got these tablets as well and ran into the same issue and followed those direction and here is what happened to me
C:\Users\******\Downloads\platform-tools_r28.0.1-windows\platform-tools>adb shell dpm set-device-owner com.meraki.sm/ .DeviceAdmin
usage: dpm [subcommand] [options]
usage: dpm set-active-admin [ --user <USER_ID> | current ] <COMPONENT>
usage: dpm set-device-owner [ --user <USER_ID> | current *EXPERIMENTAL* ] [ --name <NAME> ] <COMPONENT>
usage: dpm set-profile-owner [ --user <USER_ID> | current ] [ --name <NAME> ] <COMPONENT>
usage: dpm remove-active-admin [ --user <USER_ID> | current ] [ --name <NAME> ] <COMPONENT>
dpm set-active-admin: Sets the given component as active admin for an existing user.
dpm set-device-owner: Sets the given component as active admin, and its package as device owner.
dpm set-profile-owner: Sets the given component as active admin and profile owner for an existing user.
dpm remove-active-admin: Disables an active admin, the admin must have declared android:testOnly in the application in its manifest. This will also remove device and profile owners
Error: Invalid component com.meraki.sm/
C:\Users\*******\Downloads\platform-tools_r28.0.1-windows\platform-tools>adb shell dpm set-device-owner com.meraki.sm/ .DeviceAdmin
I sent in a Help Case to see what the correct thing to do here is