Is there a way to see a detailed list of user name conflicts while conducting domain federation in Apple Business Manager?

Not that I have ever found. You only get the number of accounts, no names.

My recommendation... Get chummy with your mail administrator. My usual process is to reach out to the mail admin in advance of toggling Federation on. This way, I have him do a mail trace and provide me with a report of all of the addresses that receive the notification from Apple. I then immediately send those people an email explaining why they got the email from Apple and the process they should take to migrate their account to free up the Apple ID for corp use.

Also, as a reminder, if one of the Apple IDs was used to make purchases, those purchases go with the user when she changes the Apple ID. You cannot transfer the licenses to the enterprise. This may have significant cost to your organization or institution if you have been gaming the licensing system by using a single Apple ID across multiple corp devices (for paid for software).

I've gone into many schools and it is usually Proloquo2go that is the culprit. Years ago, the school bought one license on an Apple ID and then used that Apple ID on many devices. If you are relying on that process and you force conversion of the IDs to managed IDs, you will also need to purchase a fresh set of licenses through ABM/ASM for the correct number of seats. This is the proper way to license the software but for some orgs they may not be expecting the extra licensing fee. Remember, managed Apple IDs cannot make purchases and thus cannot be associated to app licenses.

Hope this is helpful. Good luck,

Reid

Remind them that the email address/domain belong to the org and not the user. They will have an opportunity to change the email address they are using for the Apple ID.

Also, send out comms before you pull the trigger. It makes a big difference.