I have successfully submitted a driver on the Microsoft Partner Center Dashboard.
I have received an email from microsoft saying that we can download the driver ("Your submission for your driver is complete and ready for download.")
, and a link to follow: https://partner.microsoft.com/en-us/dashboard/hardware/driver/13790515835746598
But I cannot download the driver package containing the signed driver. There is no link to do this on any page I have seen on the dashboard.