Thank you! Hoping AT&T changes their minds and will turn on dual SIM... seems to just be turned off by the carrier.It doesn't allow dual SIM in the US at all. One of the first things I looked for once my AT&T S21 Ultra was unlocked. Even flashing U1 firmware doesn't allow that. However, it does completely convert the phone to the Unlocked version of Samsung's firmware, so your updates won't come with AT&T bloatware, only Samsung apps.