Is anyone aware of a way to transfer ownership or a board? Even a possible workaround solution?

Yes! Love this idea and hope it gets more attention! 

Proofs should always have a decision made on them as a best practice. I would advise project owners to go back to the items on your list from closed projects and make decisions on those proofs so they fall off the report. 

This is what you need:  

I would try Project Completion is not equal to 100% or Proofing Decision is equal to pending and see if either of those give you the results you are looking for. 

Are the externals set up with user accounts within Workfront? If not that would be the first step. Then, check the access level permissions and make sure they are allowed access Dashboards. I would reach out to WF support for guidance on APIs. You may need Fusion if you do not have it already.

I don't know your system set up so I can't give you an exact step by step but.  1. Check the users' access level and make sure they have dashboard view permissions.  2. Set up and "External Users" group or team and add the users to it 3. Try sharing the dashboard again to those users once you have c...

Oh! Our external users cannot access ProofHQ so the above steps is what can be done within Workfront as a work-around. A deadline date column can be added to the native Workfront report to meet your needs. 

While you were in the edit view of the report, open the report option and enter in someone you know would have outstanding proofs into the "Run this report with the Access Rights of:" field. When you close you should see what that user would see if they have pending proofs. Just make sure you remov...

This can be achieved natively by using a Proofing Report. Your filters will want to be something like the following: Proof Approval> Awaiting Decision = True Approver>Name = $$USER.ID   Columns can be adjusted to include a link to the document and deadline date.    Add it to a dashboard and pin to t...