Prevent users from joining a meeting
Add a setting to prevent users who are not a member of the Team/O365 Group from joining the Teams meeting. This setting should exist in the Outlook client as well as the Teams client, web app, and mobile app.
Similarly, prevent people who were not invited directly by the meeting organizer from joining the meeting. (e.g., meeting invite was forwarded or meeting link was copied and sent to user who was not directly invited).
Marcelo Fresca commented
Analyze how to create private meetings in Teams, ensuring that, even if a user who was not invited to the meeting received the link, he / she is unable to enter it.
It would also be useful to be able to prevent users from rejoining a meeting, if their presence is required only for a part of the agenda. For example enable the meeting organizer to enforce Lobby even for internal users would solve a lot.