You can use the advanced mapping in Templates to convert the SAMAccountName value to all lowercase. Once you have adjusted the Template, you can then apply the template in the workflow stage phase.
From our On Demand Migration Current - Active Directory - Directory Sync Advanced Mapping Guide on using lower function:
https://support.quest.com/technical-documents/on-demand-migration/current/active-directory---directory-sync-advanced-mapping-guidelower- Purpose: This method is used to convert all characters of a given string value to remove capitalization. This can be helpful prior to comparisons as well as in other situations which require lowercase wording. The return value is a new string containing the lowercase string.
- Syntax: lower(value)
- Example: The customer wants the target DisplayName to be all in lowercase.
Target Attribute : DisplayName
Value : lower(S.DisplayName)
Condition : Null