Each brokerage account has a dedicated cash account linked to it for the client. Thus, cash deposits sit on a cash account insured up to 100K. Then, assets are within the brokerage account in SPVs usually.
Maybe in other brokers, have a “cash account”, if you are speaking about a bank account (not mentioning those brokers in here).
Please read the above Help links, it’s better explained there. Many brokers don’t have an individual cash account for each customer. There is an omnibus bank deposit account, as probably you already saw when transferred money to T212.
Bottom-line: We don’t have a personal/individual bank account and due to that no personal IBAN.