Since November 2022 Microsoft requires that you purchase a Cross Tenant User Data Migration license in order to use their cross tenant migration services for Exchange or OneDrive. But there is very little information about this license type available online. Here are the basic details for this license type for anyone who is curious:
SkuId: 946ce899-873d-44bb-9d8b-671870cbfdbf
SkuPartNumber: Cross_tenant_user_data_migration
ServicePlans: {SHAREPOINTONLINE_T2TODMOVE, EXCHANGEONLINE_T2TMBXMOVE}
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