Yes, presenter and producer of live event must sign in with account.
For the attendees, they can join live event without sign-in information if the live event is public.
For more details, please refer to this article: https://learn.microsoft.com/en-us/MicrosoftTeams/teams-live-events/plan-for-teams-live-events#who-can-attend-create-and-schedule-live-events.
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