Update 3: OH6 Update
If you’re looking for root on the latest OH6 update, the UniKernel v8-0002 is reported to be working. We don’t know about the Aou kernel linked below though, chances are good for it to work as well, you may try. Below is download link for UniKernel if you need, along with installation instructions:

[icon name=”download” class=”” unprefixed_class=””] Download UniKernel v8-0002
[icon name=”hand-o-right” class=”” unprefixed_class=””]  Installation instructions (KNOX counter will be tripped)

  Update 2: Replaced UniKernel with Aou kernel by Aou, which seems to have fixed the in-call sound and battery life (deep sleep) issues. Thanks D Dougherty for the info. 
  Update: Looks like the custom sboot.bin isn’t playing very well, causing issues with Calls and Fingerprint sensor. Take a look at the comments section below for details.

Oh, yeah! Gotta say that the 3rd party Android development community is pretty awesome. So what if Ping Pong Root was patched, folks over at XDA have now come up with a new method to root the T-Mobile Galaxy S6 that doesn’t trips the KNOX counter.

Exactly, boy! You read it right, developers did something with the sboot on T-Mobile S6, such that flashing a custom kernel to it afterwards doesn’t trips the KNOX counter. Pretty amazing. Let’s just cut talk and get straight to the process for ya all waiting for this day to come.

Downloads
Download Odin 3.10.6

T-Mobile S6 G920T files:

T-Mobile S6 edge G925T files:

Instructions

NOTE: Make sure you follow the exact process as detailed in the guide below, or else you’ll trip the knox counter.

  1. Download Odin 3.10.6, Aou kernel, TWRP recovery and SuperSU v2.49 from the downloads section above. And transfer the SuperSU .zip to your phone’s storage while keeping other files on your PC.
  2. Download the sboot.bin for your T-Mobile S6 (G920T) OR S6 edge (G925T).
    └ Be very cautious. Download sboot.bin file meant for your model number only.
  3. Open Odin 3.10.6 on your PC.
  4. Boot your T-Mobile S6 into Download mode:
    1. Switch off your phone.
    2. Press and hold “Home + Power + Volume down” buttons for a few seconds until you see a warning screen.
    3. Press Volume Up on the warning screen to accept it and boot into Download mode.
  5. Once your T-Mobile S6 is in download mode, connect it to the PC with a USB cable. The Odin window on PC should detect the phone and show an “Added!!” message.
  6. Now click on the BL button on Odin window and select the sboot.bin file that you downloaded above (specific for your device model number).
    └ Note: DON’T play with any other options on the screen. You’re only required to connect your Galaxy S6 and select the SBOOT file in BL tab.
  7. Click the Start button on Odin and wait for it to finish the process. Once it has finished successfully, you’ll see a pass message on the Odin screen and your device will automatically reboot. You can close Odin now.
  8. Once phone is booted. Power off and boot into download mode once again.
  9. Open Odin 3.10.6 again. And this time click on the AP button and select the Aou kernel .tar file that you downloaded above specific for your device.
    └ Note: (again) DON’T play with any other options on the screen.
  10. Click the Start button on Odin. Your device automatically reboot once Odin is done with its process. Close Odin.
  11. Now once again, reboot your your device into Download mode and flash the TWRP recovery .tar similarly like you flashed the kernel in Step 9 above.
  12. Now boot into TWRP Recovery:
    1. Switch off your phone.
    2. Press and hold “Home + Power + Volume Up” buttons for a few seconds and soon as you see Galaxy S6 logo on screen, release the buttons. You’ll boot into TWRP recovery.
  13. Once in TWRP recovery, flash the SuperSU .zip file that we transferred to your phone in Step 1.
    └ In case you aren’t able to flash SuperSU via TWRP, then just grab it from Play Store (link), it might work.
  14. Reboot your phone.

That’s it. Look for SuperSU app when your phone boots. And to verify KNOX status, boot back into download mode and check info in upper left part of the screen. It should look like “KNOX WARRANTY: 0 (0X0000)”

Cheers!

via xda (1), (2)