[Sprint Galaxy S 5 General] vrobo:
thanks tet1 and djohne !

I've successfully unlocked the S5 Sport (G860P) for international SIM cards using the SM-G900P_NI3_ROOTED_ODEXED.zip and NG3 firmware. My phone even had a fresh firmware - Android 6.0.1 G860PVPU2CPD1 !

Please note that I did everything wrong, you should not follow my steps, and if you follow my steps you could brick your phone! So proceed only if you have an extra G860P handy and don't care about bricking one. I don't really understand how it worked. Also note that I'm using Linux so was flashing the phone with Heimdall, not Odin.

1) do a factory reset using the stock recovery (Vol.Up+Home+Power)

2) reboot to "Download" mode (Vol.Down+Home+Power) and install TWRP

heimdall flash --RECOVERY twrp-20171204-kltesprsports.img --no-reboot

3) reboot to TWRP, do a factory reset again ("Wipe" button)

4) turn off phone, copy SM-G900P_NI3_ROOTED_ODEXED.zip and SSU.apk to the SD card, insert SD card into the phone, boot TWRP again (Vol.Up+Home+Power).

5) in TWRP go to "Install" and install the SM-G900P_NI3_ROOTED_ODEXED.zip, clean cache&dalvik

6) reboot to "Download" mode (Vol.Down+Home+Power), and flash the G860PVPU1ANG3 firmware

THIS IS WHERE YOU COULD BRICK YOUR PHONE and it worked for me only by luck. ALSO READ THE NOTE AT THE BOTTOM OF THIS POST!

heimdall flash --MODEM modem.bin --APNHLOS NON-HLOS.bin --ABOOT aboot.mbn --BOOT boot.img --TZ tz.mbn --CACHE cache.img.ext4 --RPM rpm.mbn --SBL1 sbl1.mbn --DBI sdi.mbn --RECOVERY recovery.img --SYSTEM system.img.ext4 --no-reboot

the command above did not succeed, and the phone showed an ABOOT error: "Error SW REV CHECK FAIL : [aboot] Fused 2 > Binary 1", (because preinstalled firmware 6.0.1 was newer than the one I was trying to install - 4.4.4). So I modified the heimdall command and tried to flash again without ABOOT part: (but first reboot the phone to Download mode again)

heimdall flash --MODEM modem.bin --APNHLOS NON-HLOS.bin --BOOT boot.img --TZ tz.mbn --CACHE cache.img.ext4 --RPM rpm.mbn --SBL1 sbl1.mbn --DBI sdi.mbn --RECOVERY recovery.img --SYSTEM system.img.ext4 --no-reboot

the command above did not succeed too, and this time the phone showed a TZ error. I have rebooted the phone to Download mode again, removed the TZ part from the command and tried to flash for the 3rd time:

heimdall flash --MODEM modem.bin --APNHLOS NON-HLOS.bin --BOOT boot.img --CACHE cache.img.ext4 --RPM rpm.mbn --SBL1 sbl1.mbn --DBI sdi.mbn --RECOVERY recovery.img --SYSTEM system.img.ext4 --no-reboot

this time I got a CACHE error. I decided not to continue with the flashing and tried to boot the phone, and surprisingly it booted!

7) now I had a million of errors like djohne said, you just have to press "OK" a million times and quickly navigate the menus before new error message appear. Go to settings & allow installation of unknown apps & open the file manager & install SSU.apk from the SD card.

8) somewhy the SSU.apk did not unlock the SIM on the first try, but I've just pressed the Unlock button again and on the second try it showed that the SIM is unlocked.

9) Then I've turned off the phone, booted the recovery and cleaned cache, and booted the Android. There was no "invalid SIM card" error anymore, but the mobile network was not detected too. I opened settings -> mobile networks -> changed the network mode from CDMA to GSM, and it worked!

10) [purely optional step]

I've flashed TWRP again, opened TWRP, cleaned cache, started Sideload and installed LineageOS from the computer by "adb sideload lineage-....-kltesprsports.zip". Rebooted to LineageOS, and had to change the mobile network from CDMA to "GSM/WCDMA preferred" again. The SIM still works, as well as 3G internet.

NOTE:

Settings -> About phone shows "Baseband Version" : "G860PVPU1ANG3", so it somehow downgraded from the firmware version that was installed on the phone. I think that flashing all partitions in step 6) was not necessary, and it could have worked with flashing only the --MODEM partition. But I could be wrong!