Hello, the attached picture is what you'll see when you don't allow anonymous users to join a Teams meeting. That settings is as Vasils mention located here https://docs.microsoft.com/en-us/microsoftteams/meeting-settings-in-teams#using-the-microsoft-teams-...

Recently more granular settings were made available which is also described in the above link.

Anonymous users are either not signed in to their Teams accounts or are simply not using a M365 account (no AAD identity) or a Microsoft account but rather yahoo.com or gmail.com.