This change is published in the Office 365 message center as MC716008.
No label: All participants who are part of the organizer’s organization.
External: All participants who are external to the organizer’s organization but have a trusted relationship with the organizer or their organization.
Unverified: All other participants will be seen with this label. This will include Microsoft Entra ID users who belong to organizations that do not have an explicit external access setup with the organizer’s organization, Microsoft Account (personal) users, users who are not using any Microsoft ID while joining meetings, and others.