Teams new and MTO (Multi Tenant Organization)
Microsoft is moving towards a new optimized collaboration and administration for organizations operating multiple M365 tenants. New Teams client is supporting this feature.
Nevertheless, there are (today in public preview) limitations to MTO, which might be removed over time.
Self-service of multitenant organization functionality is limited to a maximum of five tenants and 100,000 internal users per tenant. To request a raise in these limits, submit a Microsoft Entra ID or Microsoft 365 admin center support request.