Do want to change this Azure AD attribute below(it doesn't exist on Exchange online side)? It cannot be changed:
Because, you need to change it from Exchange online, but Exchange online doesn't exist such attribute.
For Exchange online, there only exist "Notes" for distribution group. "Description" is an attribute for Office 365 group:
If you want to change the Description for an Office 365 group, you can use command below:
Set-UnifiedGroup OG1 -Notes Test12345
In sort, there doesn't exist Description attribute for an Exchange online distribution group.
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