[Samsung Galaxy S21 Ultra] K0mraid3:
USE UPDATED POST, HERE!

THIS POST IS NOW ONLY REFERENCE ONLY - WILL BE DELETED SOON.

Well I figured I'd make a quick How-To on how I successfully Carrier/Sim unlocked my Samsung Galaxy S21 Ultra 5G running the NEWEST Android update on bootloader 5 (USQU5BULJ)released in January of 2022.

***This does NOT trip Know and does NOT require a root or a paid service. ***

****Also Note - This is the process I took, you may find some of these steps are not needed but for the purpose or recreating my results, I'll be posting my exact process.

****This has ONLY BEEN TESTED ON SNAPDRAGON BASED SAMSUNG GALAXY S21 ULTRA 5G SM-G998 U & U1, if you try it on a different model or phone you may (and likely will) receive different results!!!!

Here's what you'll need:

•ANY (activated or not) Sim from the carrier you wish to switch too.(or a way to replicate the carriers cert from one)

•A computer

•Patched Odin

•BOTH the NEWEST U & U1 ROMs/Firmware - theres a full post on these and how to flash them here on XDA (Reminder for myself or mod to link it) or visit SamFW.com, it has both Odin and the ROM/Firmware files you will need.

•Android ADB platform tools (You can find them on the official Android Developers page here or use any ADB software of your choice, fastboot is not required or used in this process.(Google "Android Developer Platform Tools" to get them from the official Android devs page. )

STEP 1:

So let's presume you have a Verizon or T-Mobile carrier locked phone, if you look at your baseband, which you can find in Settings > About > Software Info, you should see this "SM-G998Uxxxxxxx"

*****IF YOU SEE "SM-G998U1xxxxxxx" STOP - Skip to step 2******

Head over to your preferred site to get stock Samsung Roms (Refer to link above if you don't know where to find) and download the U1 XAA rom and the U rom of the CARRIER YOU WISH TO USE. IMPORTANT! MAKE SURE YOU DOWNLOAD THE "U" ROM FOR

BOTH

THE CARRIER YOU WISH TO SWITCH TO

AND

THE U1 UNLOCKED ROM.

Put you device in download mode (Hold Vol up and Vol down and plug in the USB, which should be connected to your PC and now your phone at this point.)

Flash the U1 XAA Rom, place appropriate files in appropriate places in Odin, when you get to CSC, DO

NOT

use the "HOME_CSC" use the other.

Leave the rest of Odin settings alone and hit Start, wait for it to finish and reboot.

Step 2:

Once the phone boots, return to Settings>About>Software and confirm you are using the XAA rom by looking at Service Provider Software Version and it should say something like "SM-G998U1_XAA blah blah blah" you just want to see the U1 and XAA.

Now put in the Sim from the carrier you desire. A pop-up should appear prompting you to restart your device. Follow the prompt.

!MOST IMPORTANT STEP!

BEFORE the device fully restarts, force it into RECOVERY MODE, I was able to achieve this by holding the power and Vol Down buttons at the same time, starting to hold the directly after the "Samsung" Logo fades away upon initial restart. If you have trouble getting into recovery please comment below.

Once in recovery, use the volume keys to navigate to "Clear Cache" select and execute. Now go to Factory Data Reset/Wipe, select and execute. It should be the option directly above "Clear cache".

Once done, go up to "Reboot to Bootloader", Select, Execute.

AGAIN, Very Important step,you MUST interrupt the boot process again and force the phone BACK into

download

mode this time, so once the phone attempts to reboot, you need to hold the Vol Down and Vol Up buttons at the same time and the USB

MUST

be already plugged in.

We should now be back in download mode and be on the U1 rom. We have verified all of this in the steps above.

STEP 3:

Now it's time to flash the ROM from the carrier you wish to use. Make SURE you have a Sim from that carrier inserted during this process. It doesn't need to be a working or activated Sim, just simply one from the carrier you wish to have your S21 work on.

Flash all items as you did earlier, but using the "U" ROM for your desired carrier as described above. Same deal with CSC, DO NOT use the "Home_CSC"

BE SURE that you use the USERDATA file if there is one for your carrier. Very important to have the phone working properly.

Start the Odin flashing process.

Phone will Auto-Reboot.

Done!

You should now be on the carrier you wish to use. This can be (in theory, test at own risk) replicated for ANY carrier supported by Samsung, and, I should soon find out if it will lead to what my original goal was, a bootloader unlock on the QualComm SnapDragon variant of the S21 and future Galaxy devices.

If you have any issues please comment below.

PoC, results after doing above process.

Good luck.

-k0mrade

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