What DomainName to provide to Get-AzEventGridSubscription for custom topics not in a domain?

In Azure PowerShell module version 13 and later, the Get-AzEventGridSubscription cmdlet requires the DomainName parameter when querying subscriptions associated with Event Grid Domains. The DomainName parameter is irrelevant and should not be necessary for custom topics that are not part of a domain

You can work as follows:

Try by passing an empty string ("") or $null for the DomainName parameter. Custom topics should not have a domain, so this might bypass the requirement. Try the following PowerShell command:

Get-AzEventGridSubscription -ResourceGroupName "yourResourceGroup" -TopicName "yourCustomTopic" -DomainName ""

If the PowerShell cmdlet behavior persists, consider using the REST API or Azure CLI as an alternative.

az eventgrid event-subscription show --source-resource-id /subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.EventGrid/topics/{topicName}

Thank you for the insights.

I've tested various values passed to the DomainName parameter:

Parameter not provided at all: Cannot process command because of one or more missing mandatory parameters: DomainName.

$null or "" value provided: Cannot bind argument to parameter 'DomainName' because it is an empty string.