Find My iPhone

I'm trying to reset my iPhone X because I am not able to connect my new iCloud account to my phone, but I am unable to sign out of the old iCloud account. Every avenue I try always results in needing the password/access to the old iCloud account.

I do not know the password to my old iCloud account, the email that is connected to that iCloud account does not exist anymore. I have tried every password combination that it could be, which has lead to that account being locked, and Apple will contact that email with a solution (which is not possible due to it not existing anymore). It's a vicious cycle.

I need to find a way to be able to escape the old iCloud account without the password.

Please and Thank You.