Just curious, why buy the AT&T Model at full price when the Sim-free Model for the iPhone 11 Pro Max is available to pre-order? And they do the same exact thing?
Anyways even if you buy the AT&T model outright, it will be unlocked, this is if you buy it directly from the Apple store. If purchased from the AT&T store, I believe it's locked for 60 days and then you can request an unlock afterwards.