Yes, you can use a Webex RoomKit Plus, or any other endpoint running the similar CE software code as a Standalone endpoint.
Have a look at the "SX20 as standalone" thread for information on the configuration required.
PS I've moved your discussion to the TelePresence section of the Community where these devices and configurations are more actively discussed than in the Webex section (which is more for the Webex Cloud platform, and not the hardware), and where you will find the previously mentioned thread.
Wayne
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