Thank you for your reports on this. Microsoft is working to re-enable secure support for virtual camera apps on the Mac client. Until then, you can use the virtual camera in Teams in Chrome or Edge on your Mac.
We will update here and at the link below when there is more news: https://docs.microsoft.com/microsoftteams/troubleshoot/teams-on-mac/virtual-camera-doesnt-work-macos.
An error occurred while saving the commentsarimarton commented
@Joerg K. You're answer is undeservingly unnoticed, it works, thanks so much! People check out Joerg K.'s comment at January 21, 2021 8:00 AM - it's a good workaround.