[jmmejia4670]

Dear friends, 
I am trying to obtain boot.img to patch via Magisk and root my Samsung SM-J337A. 
The problem I face is that after much research I'm still not sure if I found the compatible boot.img for my device. 

Originally, the SOFTWARE INFORMATION for my phone is as follows:

*** SOFTWARE INFORMATION 

Android version
8.0.0

Samsung Experience version
9.0

Baseband version
J337AUCU3ARJ1

Build number
R16NW.J337AUCU3ARJ1

I wrote it down, but not all of the SOFTWARE INFORMATION. Only the information shown above. 

But after a few days my phone received an update. 

After update this is the SOFTWARE INFORMATION:

*** SOFTWARE INFORMATION 

Android version
8.0.0

Samsung Experience version
9.0

Baseband version
J337AUCU4ARL1

Kernel version
3.18.14-13465503-QB20918127
DPI@21HHAF04 #1
Tue Dec 4 18:55:55 KST 2018

Build number
R16NW.J337AUCU4ARL1

Security Enhancements for Android status
Enforcing
SEPF_SM-J337A_8.0.0_0007
Tue Dec 4 19:06:00 2018

Knox version
Knox 3.1
Knox API level 25
TIMA 4.0.0

Service Provider SW ver.
SAOMC_SM_J337A_ATT_ATT_OO_0033
42007dcd9bb4c579
ATT/ATT/ATT

Security software version
ASKS v1. 4.5 Release 180123
FIPS BORINGSSL v1.2
SMR Dec-2018 Release 1

Android security patch level
December 1, 2018
***
Perhaps I found the ROM for the original software. These are all the file names:

AP_J337AUCU3ARJ1_CL13465503_QB20325568_REV00_user_low_ship_meta.tar.rar
CP_J337AUCU3ARJ1_CP11051172_CL13465503_QB20325568_REV00_user_low_ship.tar.rar
BL_J337AUCU3ARJ1_CL13465503_QB20325568_REV00_user_low_ship.tar.rar
CSC_OMC_ATT_J337AATT3ARJ1_CL13465503_QB20325568_REV00_user_low_ship.tar.rar

COMBINATION_FAC_FA80_J337AUCU3ARI1_FACFAC_CL13704061_QB19717843_REV00_user_mid_noship.tar.rar

However, for the updated system I only find the combination file. Well, at least that is what I think I found. This is the file name:

COMBINATION_FAC_FA80_J337AUCU4ARK1_FACFAC_CL13704061_QB20833319_REV00_user_mid_noship.tar

I already extracted and patched the boot.img for this latest 4ARK1 combination file, using Magisk. But I'm not sure if it would be compatible. 

Can you tell me please?

[Noblex]

use Sp flashtool or Nck dongle to backup your ROM, so after that you can get your phone boot.img

[X3non]

Dear friends, 
I am trying to obtain boot.img to patch via Magisk and root my Samsung SM-J337A. 
The problem I face is that after much research I'm still not sure if I found the compatible boot.img for my device. 
...
Can you tell me please?

much preferably, flash the previous firmware build onto your device then use boot.img from the original firmware
you can flash using odin @ https://www.hovatek.com/forum/thread-519.html ; hopefully your phone will allow for downgrading