Explanation of the error
This Salesforce error can occur when deploying DigitalExperienceConfig metadata. Specifically, it refers to the custom URL of the configuration.
This occurs if the custom URL is not valid. If the custom URL is set to the root or blank, this is considered not valid by Salesforce.
Resolution
To resolve this, you'll need to make sure the Digital Experience bundle has a custom URL, as a blank custom URL is not valid. You'll also need to make sure the custom URL is valid for your org.
Try adding the URL and attempting deployment again.
If this doesn't change anything, please send a message to our support team, who will be happy to help.