Additional meeting and call-related features and issues within Microsoft Teams for business
The problem is ALL audio options are greyed out whilst the audio driver is crashed out (red cross on speaker icon in system tray), so changing options etc isn’t possible.
Another workaround besides stripping the software off and renaming any config folders in the user profile is to start the meeting on another device and then transfer to the affected device.
However for a user at home on a laptop without Teams on their phone or another device (such as in my case) the workaround isn’t possible.