Hi @Pedro Osório ,
the accounts and permissions used by Azure Entra Connect are listed here:
Accounts used for Microsoft Entra Connect
There is a difference for installation and sync tasks of Azure Entra Connect.
AD DS Connector account: Used to read and write information to Windows Server AD by using Active Directory Domain Services (AD DS)
AD DS Enterprise Administrator account: Optionally used to create the required AD DS Connector account
For the sync task of Azure Entra Connect you need the permission to read and write in your on-premises AD. That doesn't mean an on-premises Domain Admin is required.
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Regards
Andreas Baumgarten