In October 2021, Microsoft will enable the Azure AD email one-time passcode identity provider in tenants. SharePoint Online and OneDrive for Business will use the provider to control access for external people to its resources. The net effect is that Azure AD will create guest accounts for external sharing recipients. Even though guest accounts need to be managed, there’s lots of good reasons to use guest accounts, as we describe here.
https://office365itpros.com/2021/08/17/sharepoint-online-embraces-azure-b2b-collaboration-external-s...
