A year after announcing Teams shared channels, Microsoft is preparing to release the code into public preview in March 2022. The new collaboration mechanism uses Azure AD B2B Direct Connect instead of guest accounts, meaning that external members of shared channels use credentials issued by their home tenant to gain access. You’ll need to configure a cross-tenant access policy to allow shared channels to work externally. Once that’s done, the collaboration floodgates open.
https://practical365.com/microsoft-prepares-debut-teams-shared-channels/
