[AT&T Samsung Galaxy S7 Guides, News, & Discussion] najoor:
Just so everyone has realistic expectations, a root method without the engboot will likely not happen in the "next few days" or any time soon and here is why:

The leaked engineering boot image is a T-Mobile image for G935TUVE2APD7. TMO is known to impose the least amount of restrictions on their ROMs and that is probably why this kernel is working for all carriers (TMO is the hero of the day again!) The way the boot process in Marshmallow works is through a trust chain. What it means is that the bootloader checks the integrity of the boot image (aka kernel) to make sure it is unaltered and properly signed by Samsung. If that fails the phone does not boot and/or your knox flag is tripped. If that passes, the kernel is loaded and the kernel in turn checks the integrity of the system partitions (known as dm-verity). If that fails you get a bootloop.

With an engineering kernel this last step is disabled because engineers keep changing the system files as they develop a release. That is why this engineering boot image allows the injection of SuperSU, and that is why this root method can work. If you flash a user (non-engineering) image, such as the G935U boot image, it immediately detects the changes in the system and bootloops.

So you see, it is a fundamental protection that did not exist in previous Android versions and that is why it is unlikely that a root method on the non-engineering version is accomplished any time soon; you cannot touch the system because the kernel checks it and you cannot touch the kernel because the bootloader checks it. So the only possible options are as follows:

1- The bootloader is unlocked by the carriers so modified kernels can be loaded (not gonna happen). This is how nexus phones are rooted.

2- Another (engineering?) kernel without dm-verification (with better performance) is leaked/released that allows changes to the system, hence root. This is how the present root for S7 has been accomplished.

3- A vulnerability is found in Android system that allows a process to obtain root after the phone boots up. This is much more likely. In fact this is how Xpreia devices such as Z3/Z4/Z5 recently got root. This is also how towelroot worked in Kitkat which didn't have dm-verity activated. The problem in marshmallow is that this kind of root has to be temporary (should disappear after a reboot) and you will have to stay away from changing the /system otherwise the phone barfs upon the next reboot because of dm-verity.

4- A vulnerability is found in the kernel or bootloader code that is exploited to change /system. For that to happen someone has to sit down and dissect the kernel/bootloader code and read and analyze it line by line. I only remember a few times this ever happened during the exciting days of Android (when a Samsung phone didn't look and feel like an iphone). That is how Jellybean got rooted on early Note 3 devices. No one has the time or interest to do that anymore and people at that level of skills already have a very busy life. As valuable as their contribution is, the custodians of this current root method did not do it either. They used method 2 above.

So stay with the unlocked ROM and be happy for now. I posted a small analysis of the situation here: http://xdaforums.com/att-galaxy-s7/how-to/root-s7-att-g930a-g935a-t3410538/post67633470#post67633470 Reasons for rooting after flashing the unlocked ROM are few, if any.