I tried this method with my device and worked flawlessly.
-If you already updated your firmware to ANG2 and didn't get root, you can downgrade to ANE2 (WON'T TRIP KNOX), root, and then follow this method. UPDATE: Or you can do it in a much easier way with THIS AWESOME AND EASIER METHOD (Post & Method by my friend @wajiman)
-Make sure you have your S5 already rooted. (You can make this with Towelroot: https://towelroot.com/, this method will keep Knox 0x0) (Thanks @geohot for towelroot)
-Make sure of having at least 70% battery for security issues.
-Make sure you have BUSYBOX installed.
-Make sure KNOX is DISABLED.
-Make sure of having USB DEBUGGING ENABLED on developer options.
-Disable reactivation lock if it's switched on.
-I'M NOT RESPONSIBLE FOR ANY DAMAGE/BRICK ON YOUR DEVICE, THIS STEPS ARE 100% CORRECT, BUT IF YOU DO SOMETHING WRONG IT'S YOUR FAULT.
2. Extract the md5 file and copy it to your EXTERNAL SDCARD.
3. Flash it with MOBILE ODIN PRO. (YOU NEED THE PRO VERSION OR YOU WON'T KEEP ROOT)
-Make sure you select the file in "Open File"
-Make sure you select the "Reboot into download mode after flashing" (THIS IS VERY IMPORTANT!)
-DO NOT select the Wipe Dalvik Cache Option. (As some users are reporting that probably Mobile ODIN Pro has a bug on flashing boots straightly into download mode instead of flashing, didn't happen to me though)
-Make sure you have the "Everroot" option ticked (FOR KEEPING ROOT)
4. After flash, you should now be on Download Mode, connect your device to your PC and on Odin, flash this 2 files:
Bootloader ANG2: BL_G900FXXU1ANG2.tar.md5 https://www.dropbox.com/s/tdiu7rc3tb...U1ANG2.tar.md5
Modem ANG2: CP_G900FXXU1ANG2.tar.md5 https://www.dropbox.com/s/rl3gh2ppvi...U1ANG2.tar.md5
-On odin place the bootlaoder on BL and modem on CP.
-Make sure Re-partition is NOT TICKED.
-Make sure Auto Reboot is NOT TICKED.
-Make sure F. Reset Time IS TICKED.
5. After Odin finishes flashing, disconnect your device and BOOT INTO RECOVERY. (Home+Vol Up+Power)
6. On recovery, wait until it finishes applying the csc files.
That's it. Any question on the comments. If I can answer it, I WILL.
Please press that THANKS BUTTON IF THIS HELPS!
You can also "buy me a beer" if you really want to, I'm currently unemployed so you would seriously help me out... "DONATE TO ME" button is on the left under my username,
"You probably paid $500US for your phone, think in the value that's added with root and this method."