unlink locked ubisoft account

Apparently, I have an old (locked) Ubisoft account linked to my xbox live account which is preventing me from linking my new Ubisoft account to my Xbox Live. That Ubisoft account is associated with an email that has not existed for years. I'm not able to log into the old Ubisoft account to unlink it, so I contacted Ubisoft support which went like this:

Ubi-Filtergrind (9/11/2022, 9:00:50 PM): Thanks for contacting Ubisoft Support. You're now connected with Ubi-Filtergrind, please allow a few moments for the specialist to acquaint themselves with your case. I will be with you shortly.

Ubi-Filtergrind (9/11/2022, 9:02:24 PM): Thank you for waiting. How may I help you today?

null (9/11/2022, 9:03:14 PM): i have a very old account that is associated with an email that is no longer available.

null (9/11/2022, 9:03:58 PM): That is preventing me from connecting my new account to my Xbox live account.

Ubi-Filtergrind (9/11/2022, 9:04:21 PM): I understand. So in this case, you would like to change the email linked to the account, correct?

null (9/11/2022, 9:04:50 PM): yes

Ubi-Filtergrind (9/11/2022, 9:05:15 PM): No worries, I can look into your case. Kindly provide the old email once again?

null (9/11/2022, 9:05:31 PM): [my old email]

Ubi-Filtergrind (9/11/2022, 9:06:34 PM): Thank you. Please give me a moment to look into the account.

null (9/11/2022, 9:07:42 PM): ok

Ubi-Filtergrind (9/11/2022, 9:10:33 PM): Thank you so much for waiting. I just wanted to check in and make sure the chat stays alive.

null (9/11/2022, 9:10:56 PM): I'm still here

Ubi-Filtergrind (9/11/2022, 9:15:57 PM): Thank you for waiting. Upon further checking, the account in question is currently locked and unfortunately Ubisoft support is unable to make any changes or updates on that said account. I do apologize if this causes any inconveniences whatsoever.

null (9/11/2022, 9:17:17 PM): ok so how can it be unlocked?

null (9/11/2022, 9:18:34 PM): it does cause an inconvenience ... see above messages.

Ubi-Filtergrind (9/11/2022, 9:21:37 PM): I do understand, however at this point, as long as you do not have access to the email linked to the account, there is no information that I will be able to work with in recovering the account linked to your Xbox live.

null (9/11/2022, 9:22:48 PM): is there another way to unlink the accounts? at this point I have paid for games that I cannot play because of this.

Ubi-Filtergrind (9/11/2022, 9:25:10 PM): I would say an alternative would be to do this through the accounts management section of the affected Ubisoft account. You may try to log in using your Xbox credentials and unlink the Xbox account from there.

null (9/11/2022, 9:26:17 PM): again ... I can't login to the accounts management screen of the ubisoft account. If I could do that we would not be having this chat ...

Ubi-Filtergrind (9/11/2022, 9:29:57 PM): I understand and I do apologize. The only way now for us to proceed with recovery would be if you had access to the email. If you do not have any questions apart from the matter, I will have to terminate our interaction.

null (9/11/2022, 9:30:27 PM): thanks for nothing

I've looked in the Microsoft account but can't find anywhere to unlink the Ubisoft account. A search for unlink ubisoft account just tells me to "simply" log into my ubisoft account and unlink it ...

It would seem that there's another way to unlink the dead Ubisoft account. Can anyone help?

:)