[Samsung Galaxy J3 (2016) Questions & Answers] Sunberg:
EDIT 3: It appears this device has a locked bootloader, which means that twrp wont work, and that device tree was a waste of time... I guess I'll just wait until someone or Samsung releases the firmware for Magisk.

EDIT 2: I have successfully built a device tree for this device using TWRPBuilder's script on github. Although it might not be fully complete, it is still a start. Note: I built using an android 8 release. Does the boardconfig.mk file still work for android 9????

I plan on comparing it with a different device tree to make sure nothing is blatantly wrong with it, but I'm not a developer so I don't know if that will help.

(Anyone willing to help me? If I could efficiently navigate the linux CLI I would probably be much faster...)

My current plan is to build TWRP for this device to back up the ROM so that I can use Magisk.

https://github.com/TwrpBuilder/twrpbuilder_tree_generator/blob/master/README.md

Link to device tree builder for those interested. Dont even ask how long it took me to realize I had to add the commands to the end of the java executive instead of typing TWRPBuilder -r recovery.img. command.

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EDIT: To those that read, Samsung has restrictions against downgrading apparently. Currently, the only way for root is by waiting for someone to share the official stock ROM. The first half of this method about getting the firmware Does Not Work I don't know about the rest...

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Hello everyone,

I would first like to say that I think this is a working method, but I want to double check with someone who has rooted before.

I have the above mentioned phone, and after a ton of research, have determined a path to rooting it through Magisk. I'm currently running Android Pie 9, on the latest stock firmware from att.

This phone does not have A/B partitioning, but has system-as-root and it will require a copy (and Magisk patched) ROM to root.

One of the main problems I have is not having the latest firmware for my device. (Don't tell me to look it up. Its non-existent on the web) I have found that Samsung's Smart Switch will allow you to obtain the official ROM.

However, to download the ROM, I have to have an outdated phone. The most recent update for my phone was to upgrade from Android 8.0 to 9.0.

I assume such an upgrade requires the whole ROM to be downloaded.

Is it possible to use an outdated ROM for my phone (Yes, I have one for android 8) and downgrade my OS so that I can then update from Smart Switch and get a copy of the current firmware to use with Magisk?

Edit: apparently Samsung has protections against downgrading. I tried samfirm but to no avail.

Anyone know of any compatible custom ROMs?

Will keep trying to root though...

I know many people will immediately say yes, but this phone is different.

There is no OEM unlock in Developer options (read more about this further!), and there is no fastboot. There is no TWRP for this phone either (some older threads on Magisk mentioned TWRP, so I am confused if I need it for rooting via Magisk)

I have discovered, that if you were to hold HOME + POWER + UP, on powerup, you can get to a warning about installing custom OSes and an option to continue.

I pressed continue.

Someone on the web said pressing up will wipe the phone, since it unlocks the bootloader.

My phone did not get wiped.

Is my phone's bootloader/OEM unlocked?

I want to know because I Think Magisk requires an unlocked bootloader.

If Magisk doesn't, I'm all good, and I am glad I can install custom OSes (not my goal, but will do if desperate)

If it does require it, I believe my hone already has an unlocked bootloader/OEM

One last note, does downgrading trip anything? I have no warranty, but I know there are other protections (like KNOX) that could affect the outcome.

(I've heard downgrading won't change anything)

Is there anything I need to turn off?

To Recap:

Downgrade OS

Update via Smart Switch to get stock ROM

Use Magisk to root my phone.

I'm simply asking if everything will turn out OK.

(Sorry for the exceedingly long post)

Thanks.