@Daniel Kaliel Thanks for reaching out.
sAMAccountName attribute should be syncing by default. It is already in list of of the attributes which sync to AzureAD.
You should consider following scenario though under which sAMAccountName does not synchronize if :
Also note, The SAMAccountName attribute, such as AADDSCONTOSO\driley, may be auto-generated for some user accounts in a managed domain. Users' auto-generated SAMAccountName may differ from their UPN prefix, so isn't always a reliable way to sign in.
For example, if multiple users have the same mailNickname attribute or users have overly long UPN prefixes, the SAMAccountName for these users may be auto-generated. Use the UPN format, such as email@example.com, to reliably sign in to a managed domain.
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