[Samsung Galaxy S21 Ultra] K0mraid3:
Here's a free 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 that was carrier locked to Verizon and now fully Unlocked.

DISCLAIMER:

*This does NOT trip Knox or Void your warranty and does NOT require a root or a paid service. **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!!!!

You can read more on how this method works to force a carrier update to your device, here, on the Official Android dev site.

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, Stock Firmware and ODIN Flashing Guide (XDA) or visit SamFW.com, it has both Odin and the ROM/Firmware files you will need.

•(Optional?) 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. Link: Android Dev Platform Tools (Official)

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"

NOTE:

It Is CRITICAL that we flash the U1 rom BEFORE putting in the desired carriers SIM, then reboot, let phone fully boot, ONLY THEN should we insert the desired carriers SIM.

Step 1b:

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

BOTH

THE "U" ROM FOR THE CARRIER YOU WISH TO SWITCH TO

AND

THE U1 UNLOCKED (XAA) ROM/Firmware.

IF YOU ALREADY HAVE U1 FIRMWARE

I.e "SM-G998U1xxxxxxx" - you can skip to step 2, but I would recommend reading through the next part.

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 the device is now showing the "U1_XAA" in the Service Provider Software Version - it should say something like "SM-G998U1_XAA blah blah blah" - you just want to see the "U1" bit.

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

! CRITICALLY

IMPORTANT STEP !

We will now initiate a reboot, but BEFORE the device fully restarts, we need to 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 them 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! We MUST interrupt the boot process again and force the phone BACK into

download

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

MUST

be already plugged in, essentially it should remain plugged in throughout this process.

We should now be back in download mode and be on "U1" as we have verified in the steps above.

STEP 3:

Now it's time to flash the ROM/Firmware from the carrier you wish to use. Make SURE you have the SIM from the same carrier inserted during this process as mentioned at the beginning. It doesn't need to be a working or activated SIM, just simply one from the carrier you wish to have this S21 work on.

Flash all items from the "U" ROM/Firmware as you did earlier, ensuring to use the "U" ROM/Firmware for your desired carrier as described above. Same deal with CSC here, DO NOT use the "Home_CSC", use the other.

BE SURE that you use the USERDATA file that comes with the "U" ROM/Firmware. Its Critical in order to get the phone working properly on the new carrier.

Start the Odin flashing process & wait.

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.

Please comment your experiences/ issues etc below. Don't be afraid to ask for clarity of something.

PoC, results after doing above process pictured in this screenshot.

Good luck.

-k0mrade

Send me Crypto if I helped?

Before process, this message would appear shortly after inserting a new SIM in testing devices:

View attachment 5530867

After preforming above procedures I now find pictured below by running this activity:

com.samsung.ssu.unlock.MainActivity

View attachment 5531069

And verify twice by checking my work in Settings>About>Software Information> Service Provider Software Version & Carrier Configuration Version.

View attachment 5531071

For anyone whos still having trouble, try following the directions on this thread. Maybe they explain it a bit better or their process omits/includes parts ive missed.

Alternative Guide To Carrier Unlocking S21

Good Luck.