
$GroupName = "<GroupName>"
1. Connect-AzureAD
2. $template = Get-AzureADDirectorySettingTemplate | ? {$_.displayname -eq "group.unified.guest"}
$settingsCopy = $template.CreateDirectorySetting()
$settingsCopy["AllowToAddGuests"]=$True
$groupID= (Get-AzureADGroup -SearchString $GroupName).ObjectId
New-AzureADObjectSetting -TargetType Groups -TargetObjectId $groupID -DirectorySetting $settingsCopy