Hello @Germain, Yves - Welcome to Microsoft Q&A and thanks for reaching out to us.
Please try adding the service principal to Directory readers using this command and see if it helps:
> Add-AzureADDirectoryRoleMember -ObjectId (Get-AzureADDirectoryRole | where-object {$_.DisplayName -eq "Directory Readers"}).Objectid -RefObjectId <object-id>
Hope this helps. and please feel free to reach out if you have any further questions.
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