I tried to do this with an app called Data Sweeper from Samsung SDSA team and at the time it was not possible.  Not sure if things have changed or not.

I'm also stuck with this and it seems that no one in the world knows how to do this.

You need to do it manually on each device.

I do it during the enrollemnt of devices.(Outside kiosk mode)

request_appops_permission android.permission.PACKAGE_USAGE_STATS
request_appops_permission android.permission.SYSTEM_ALERT_WINDOW
request_appops_permission android.permission.BIND_NOTIFICATION_LISTENER_SERVICE
request_appops_permission android.permission.WRITE_SETTINGS
afw_set_permission_grant_state net.soti.mobicontrol.androidwork allow
afw_set_permission_grant_state net.soti.settingsmanager allow

I am not aware of any mechanism that can silently set an app on an Android 8.x device to be device administrator.

Even Samsung devices with its extensive KNOX api's can only support whitelisting what apps can be added as device administrator, but not allowing and MDM to silently enabling the status remotely for a particular app.

Anyway, "device administrator" is an old concept that is destined to be deprecated gradually from Android 10 onwards.  There seems to be new MDM mechanisms defined by Google to support delegation of some specific administrator roles to one or more applications on more recent Android devices (definitely not for devices running Android 8.x firmware). with a supported device agent.   I myself am still struggling to nail down the details at the moment.