Unlocked s21 Ultra showing as "Unknown Device" and not supporting 5G or Extended Range LTE on My Mobile account

if its a TMO variant then it should already be in their system..it was branded for them after all..which if memory serves if you purchased it from another vendor it must be on their network for a certain amount of days before it can be unlocked by TMO. 40 days i believe for Post paid and a year for Pre paid or something along those lines.