I'm an ATT cellular user but I got tired of the locked bootloaders that the ATT devices have. I bought from a reputable seller on Swappa a factory unlocked unused replacement SGH-M919, since T-Mobile devices are generally compatible with ATT networks, and don't have locked bootloaders. I figured it would come with NB4, and was all prepared to Towelroot it and install a custom recovery and trip my Knox warranty counter.
Lo and behold, when I turned it on (no SIM installed yet), it has the 4.2.2 MDL firmware. <shocked happy dance> NO KNOX AT ALL!
Question 1: is there any risk of the thing downloading and installing the NB4 update if it has no SIM at all, just a WIFI connection? I've disconnected it from the wifi here at home for now. In fact, it's off.
Question 2: I need to test out the "Factory Unlocked" part of the equation in the next couple days so I can complete the sale. If I put in an ATT SIM (and configure the APN manually for ATT settings), is there any risk of it downloading the NB4?
I figure it must be connected to the T-Mobile network to get an update, but just wanted to check to make sure before I accidentally mess up this godsend.
Question 3: It looks to be straightforward from here, right? Root with CF-Autoroot, install TWRP or CWM, install ROM... right? I'm no stranger to ODIN or flashing stuff (after all the messing around needed on ATT phones... safestrap.... the horror of a locked bootloader).
FWIW I'm headed straight to Dirty Unicorns ROM. Looks like a really cool ROM. So much more to choose from on the T-Mobile M919 than on the I337 ATT phone.
If I've missed anything, please let me know. I will start a thread on my "ATT User with M919 Experience"... I've missed such a thread here, and with lots of ATT folks sick of locked up boot loaders, maybe my fumblings will help someone.
Thanks in advance for any insight.