[Samsung Galaxy S9  Guides, News, & Discussion] jdiesel5x:
Today I got up real pissed with Samsung for being so restrictive around ROM flashing, rooting, flashing custom firmware or even stock firmware, so wanted to create this post to help anybody considering to get a Samsung phone to stay away from it.

This post is not intended to recommend any specific brand or model of android phone, but to recommend the exact opposite, which brand and model NOT TO EVEN THINK of purchasing.

This post relates to Samsung Galaxy S9 G9600 model which is Snapdragon architecture, but since Samsung is coming up with a bunch of "security features" I tend to think this may be the case for other models as well. I browsed all around XDA and other sources for guides on how to root and install custom roms, and it turns out Samsung manages to have limitations for EVERY step of the way.

Getting a few facts straight

Reference post: https://xdaforums.com/galaxy-s9/sam.../rom-lineageos-17-1-s9-s9-snapdragon-t4093301

Ok, so there is a solid thread about a custom firmware and looks like several users got hands on it, but they might have been able to get passed though all Samsung security crap before it came out or before it got so tightened up. I'll list below every limitation I found:

OEM Unlock

There is a step where we need to tick OEM Unlock from the phone developer settings, it turns out Samsung has put a 7-day timer for this option to even appear listed to enable. If you do factory reset of the phone, the 7-day timer restarts. There are a few posts around on how to get passed this timer, but to me they were all crap, none of them worked. STRIKE ONE!

Bootloader unlock

After 7-days, we get the OEM Unlock option to appear, at this point you may think: Hurray!! .... WRONG! Now next step is to unlock the bootloader using an utility called CROM Services... And as you may have already guessed, did not work! I'm able to install the apk, but on launch it complains about wrong android version. (Tried with Android 8 and 10) STRIKE TWO!

There are some posts and guides claiming to be able to unlock bootloader by using fastboot utility, I can't reach to understand how, since fastboot commands rely on the bootloader to be previously unlocked (?). I least that is my understanding, correct me if wrong. Needless to say fastboot did not work for me. ADB lists my device but fastboot doesn't. There are a few troubleshoot guides around to try selecting proper USB driver from windows device manager, tried all that, tried a couple of ADB installations, fastboot didn't work.

Knox and RMM state

After some lookup in the web, Samsung incorporates some security features trying to prevent device theft and such things. For us power users this is in reality just a whole load of crap preventing us to get all the juice out of our phones.

Reference: https://www.goandroid.co.in/unlock-bootloader-of-galaxy-s9-plus-snapdragon/84688/

TWRP Recovery

Next step would be to flash a custom recovery such as TWRP with Odin or adb/fastboot, but since we are not able to unlock the bootloader in previous step, this is not doable at all. STRIKE THREE! OUT!

Fastboot utility doesn't recognize the device in download mode, so we can't send any commands to the phone.

Odin complains it is only able to flash signed stock roms, so since TWRP is not, we cannot flash it.

Rooting

Needless to say that if we don't have TWRP, we cannot flash the corresponding packages to root. Although this step may not be needed to install custom firmware, rooting has not been possible.

Stock ROM Flashing

Ok, so let's stay out of custom firmware - let's play around with stock firmwares. At this point, since flashing stock firmwares is kind of allowed by Samsung I was able to try out a couple from android 8 to 10 with Odin

Stock ROM Source: https://www.sammobile.com/samsung/galaxy-s9/firmware/#SM-G9600

But watch out! Once you get to install a specific build version, you cannot go back or downgrade to ROMS with previous Android build version. So now that I got Android 10 cannot go back to 8 or 9, this is probably because locked bootloader and unable to unlock. Here, Odin complains with FAIL! (AUTH) message.

STRIKE FOUR! EVEN OUTTER!

SIM Unlock

Ok, let's stay out of Samsung S9 G9600 model, let's crash it to the wall and throw it away to the garbage! Ok no, let's have it carrier unlocked and sell. Unlockbase is a well known and trusted sim unlock provider, I purchased a license to unlock by USB cable, but... GUESS WHAT! G9600 is not supported for unlocking operator network with this software... what a surprise!! I was able to apply for a refund and got my money back, so no worries here.

Note that flashing carrier free ROM does not unlock sim to use with any network operator.

I'll be trying to unlocking by code soon, as this is based on IMEI number, I may think this is independent to the phone model and edition, so I hope I have more luck with this option.

Conclusion

G9600 is a really crappy phone to mess around with. I may have ran low on luck with this specific Samsung Galaxy model since I got it as a gift, which is the latinamerican crappy edition. I wonder if other S9 editions and other Samsung models run with better luck than mine on this scenery...

But as a lesson to myself, I will stay away of any Samsung smartphone in the foreseeable future.