[Samsung Galaxy J3 (2017) Guides, News, & Discussio] Casper Young:
Trial & Errors Test Our Theories of Custom Modification

There are some devices that prove to be rather difficult accepting modifications and this seems to be one of them. Over the years many developers have tried to gain access and Root it. Of all the different carrier versions of this device, the T-Mobile version J327T is definately more complicated to modify for some reason. To me everything we do here on XDA can be compared to solving a puzzle. We ask ourselves how we can accomplish something and proceed with Beta Testing the idea.

So here we are. And so far we have gained little ground with this particular device. I can imagine what some developers go through as they consider ways to tackle a difficulty such as this. I think we're overlooking something basic and that is the fact that we can even get to Download Mode. Here's a little story behind my thinking. I recently had a difficulty with a couple of my devices over something called "Custom Binaries Blocked by FRP Lock". I have two Galaxy Tab A6 10.1 SM-T580s that I rooted. A couple days later I got the device manager telling me I need to reset the device. Turn it off, then back on and all of a sudden I'm in a bootloop. Sh*t! It was odd that the binary block notice came up in different ways. On one device the message came up when trying to go to Recovery Mode which was redirected to something that looked similar to Download Mode. On the other it showed up on the Logo screen during bootloop. Factory Reset didn't do anything and seemingly neither did the Download Mode, or so I thought. I would try to flash in the stock firmware and watch Odin3 initialize, then freeze up. I spent 4 hours of trial and error to return one of the devices to normal. The one that redirected Recovery Mode. The one that had the Custom Binary notice during bootloop I spent a week or two on before breaking a connection trying to de-energize it. Now it sits in a box waiting for me to fix it, I found 4 different versions of the Custom Binary Block and they all have one thing in common. You can access Download Mode and use it, somewhat.

Okay everyone what does the Bootloader do? How exactly is this part of the device tree stoping anyone from reprogrammig?

Something I noticed. During my odd little FRP Lock thing I saw that if I were to use odin3 trying to flash in any firmware that was flawed, incorrect or incompatible, Odin3 would fail in some way so basically I couldn't use it. That's worth noticing because it speeds up choosing somewhat compatible firmware to try on other devices. But it may be relevant in the difficulty with this device on the fact that we can access Download Mode. With my devices that were Binary Locked I could get to Download Mode but it wouldn't flash in ANYTHING until I flashed in the binaries. Much like this device Odin3 is not accepting much. I Rooted mine and it defaulted back to stock some time later.

Being able to access and use Download Mode says something. Seems to me this is another puzzle to figure out. I'd think that the Download Mode being accessable says two things. It wouldn't be there if we couldn't use it, Remember that fact. It also blocks a lot of things, like it's not letting anyone install custom firmware. Why not? Incompatibilities! If I could only figure out where in the programming this block is I would take it out using ADB Shell. Or I bet that If I could root it again I could run around the System Files and look for it.

I do Mental health Counseling so I have little time to spare. And I F***ing really hate coding! I think were blocked at Download Mode until compatible firmware is found. Maybe I should extract the firmware and try to find this block in the Device Tree. But that could take me months. There's someone out there that could do that in a week or less.

As far as I know when I fixed the difficulty with my tab I used FRP 4 Binary unlock or U4 Binary files which remind me of firmware repair files. Since the Download Mode (which is my focus) can prevent firmware installation such as this. Maybe it's in the Binaries to get past this.