Blocked from Migrating Entra App from Personal to Org Tenant (Production Use, Partner Account)

Sorry, no. If it used to be possible but no longer is: I can only suggest finding the right person in Microsoft who can bend the rules, reinstate the policy, or at least explain why it's no longer possible.  Perhaps JillArmourMicrosoft​ can find someone? Otherwise, as noted: having to do create a new App and transition customers over. I only deal with "internal" Customers (our CSP clients) so I don't have any suggestions unfortunately. (in my situation I'd just create a new App [with a similar but different name] and write a script leveraging the original App to deploy the new one and then use the new to remove the old. All my stuff is entirely hands-off for the client once GDAP has been granted).

Perhaps you have an account manager who can pull some strings?