SDX57M

The Qualcomm Snapdragon X57 5G Modem is the baseband chipset used in the iPhone SE (3rd generation).

it is also known as  in firmware.

iOS
1.00.04    15.4           (Build 19E241) 15.4.1        (Build 19E258) 1.60.00    15.5 beta      (Build 19F5047e) 15.5 beta 2   (Build 19F5057e) 1.61.01    15.5 beta 3    (Build 19F5062g) 15.5 beta 4   (Build 19F5070b) 15.5 RC       (Build 19F77) 15.5          (Build 19F77) 1.70.00    15.6 beta      (Build 19G5027e) 15.6 beta 2   (Build 19G5037d) 15.6 beta 3   (Build 19G5046d) 1.70.02    15.6 beta 4    (Build 19G5056c)

2.03.00    16.0 beta      (Build 20A5283p) 16.0 beta 2   (Build 20A5303i)