Crestron Appliance Authentication to join Teams meetings

Hi,

The "Crestron Teams Appliance" is that their Microsoft Teams Rooms system called Flex that you thinking of? Or is the Crestron Teams Appliance something else? 
https://products.office.com/en-us/microsoft-teams/across-devices/devices/product?deviceid=395

If it is their system running Microsoft Teams Rooms (MTR) that is a software from Microsoft running Windows 10. It is normally setup with a autologin to Windows and it will start MTR software in Windows running full screen. MTR software will use a Office 365 account to sign in to Teams and Exchange. So yes there is authentication done from the MTR.

MTR can join meetings it is invited to directly, but it could also be forced to wait in the lobby depending on the settings for the particular meeting.