@Sabir1 I agree that it is likely not just a question of Assurant but the Repairer, may be difficult to find out that information and if the case need to decide if warranty a crucial issue for you.
In my view an element of risk in using ebay for devices (particularly if an individual) seller may have a decent history that you can check though.
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 4.0,Android 12 Official Version.