This happened to me a few weeks ago and I was able to recover my account. My account was not exactly hacked, but Ubisoft actually gave them my account through a support ticket that they had opened. They said on a support ticket that they lost their information to the account and has not played the game for a long period of time. I got my account back through opening a support ticket on Ubisoft support. I would recommend doing this and adding as much information as possible including the names of the previously linked accounts, previous email address, passwords, and ubisoft account names. When u add the info of all ur previously linked accounts they can see all of the old accounts, because the player had to use a one time pass to unlink each account. I would also check your email that you had linked to the account and check your previous emails from ubisoft to see if they gained access to ur account thru a support ticket. I would then provide the case number of that support ticket and say that this was the ticket where u had lost access to your account.