I'm also working on a MS Teams integration with Webex Devices and have found some additional information that may help depending on your deployment. It doesn't specifically address the Webex Board and Navigator but once it is GA, these may help with some of your configurations.
There are settings needed in Webex Control Hub to add the MS Teams button. There was a another community post at this LINK with details about those settings. There is also additional licensing from Cisco that is required to enable this integration. Your Cisco Channel Partner should be able to help you with adding that licensing to your account.
In addition, there is some configuration that needs to be completed to enable CVI in Microsoft. Here's a LINK with more information about those configurations.
We aren't deploying any Webex Boards in our organzation yet but are working on plans that may include these devices next year so I hope this integration with MS Teams is resolved by then. Good luck @JamesHawkins.
