Thank you for patience. We’ve been working on getting clarity from EasyPost regarding this change.
You can still create a UPSDAP account with EasyPost, but it can no longer be done through their website. Instead you need to contact their support. They will then ask for contact and company details. If you already have a UPSDAP account, they may advise you to remove it. They will then add the UPSDAP account to your carriers and you can complete the wizard again to import the new account ID. We have a knowledge base article regarding this, just waiting on the publication.
We do also have a new release slated for mid April that removes the specific carrier limitation and will allow you to add any three carriers, be it the EasyPost provided ones or your own accounts.