Microsoft Enterprise E3 (with active Teams license) is a minimum requirement for Admin/Service account, when migrating Teams or M365 Groups. For any other workload (Account, OneDrive, Mailbox, SharePoint, etc.) the account does not need to be licensed, because for those we use application permissions and they are independent of the service account.
Refer to our Official Documentation below.
User Guide -> Working with On Demand Migration -> Consents and Permissions
https://support.quest.com/technical-documents/on-demand-migration/current/user-guide/3#TOPIC-2147772
