General Samsung S21, S21+, and S21 Ultra U1 Firmware (Links)

[renoflightrn]

It doesn't allow dual SIM in the US at all. One of the first things I looked for once my AT&T S21 Ultra was unlocked. Even flashing U1 firmware doesn't allow that. However, it does completely convert the phone to the Unlocked version of Samsung's firmware, so your updates won't come with AT&T bloatware, only Samsung apps.

Thank you! Hoping AT&T changes their minds and will turn on dual SIM... seems to just be turned off by the carrier.

 

[cjegan2008]

Thank you! Hoping AT&T changes their minds and will turn on dual SIM... seems to just be turned off by the carrier.

No it's hardware based. Samsung's decision, not AT&T's from what I understand.

 

[renoflightrn]

No it's hardware based. Samsung's decision, not AT&T's from what I understand.

I heard it's the carriers turning it off, but haven't seen a solid answer. Samsung still has it on their website that allows dual SIM (using eSIM and a physical SIM) - at least for the ultra.

 

[cjegan2008]

I heard it's the carriers turning it off, but haven't seen a solid answer. Samsung still has it on their website that allows dual SIM (using eSIM and a physical SIM) - at least for the ultra.

Idk. You would have to find someone on here who actually has the U1 model and see if they can use eSIM. I doubt the US versions have it. The international models probably do.

 

[renoflightrn]

It doesn't allow dual SIM in the US at all. One of the first things I looked for once my AT&T S21 Ultra was unlocked. Even flashing U1 firmware doesn't allow that. However, it does completely convert the phone to the Unlocked version of Samsung's firmware, so your updates won't come with AT&T bloatware, only Samsung apps.

One more question - How can you get the bootloader unlocked and go into download mode. No luck with my AT&T version.

 

[Geekser]

For what it's worth, I flashed the U1 firmware I mentioned with the link a few posts back - but then I also flashed the CSC file from the most recent firmware for G998U - this gives me all the ATT functionality (WIFI calling, Video Calling, etc) without the ATT Bloat. It also includes February Security Update.

 

[cjegan2008]

One more question - How can you get the bootloader unlocked and go into download mode. No luck with my AT&T version.

You can't unlock the bootloader on US devices.

 

[cjegan2008]

FYI - I found new firmware that includes February Security Patch for G998U1 - you can download it here: February Firmware for Galaxy S21 Ultra

the firmware is for a region labeled as ACG (not sure who this is - but I do know that the firmware works on my ATT S21 Ultra with no problems)

ACG is Nextech / C-Spire branded

 

[Quickvic30]

Hello all, it's been a while since I've done some flashing, used to be a flashaholic lol.

So my question is, if I use the HOMCSC will I retain all my data and have the bloat free U1 firmware or must I flash the regular CSC that wipes the phone to make the U1 firmware changes?

AKA I wanna dirty flash U1 over ATT firmware and not lose all my data.

Thanks in advance!

 

[mshouman123]

For what it's worth, I flashed the U1 firmware I mentioned with the link a few posts back - but then I also flashed the CSC file from the most recent firmware for G998U - this gives me all the ATT functionality (WIFI calling, Video Calling, etc) without the ATT Bloat. It also includes February Security Update.

I have an s21 ultra and would like to get att wifi calling mine is unlocked tmobile branded with att sim. Would you be able to let me know what steps/files you flashed to get this ?

Thanks alot !

 

[Nettwerk]

Sorry for disturbing. I have question if I flash from AT&T firmware to XAA U1 firmware via Odin will it change CSC or need to change CSC via Samkey? I know for Exynos models if you flash multi csc firmware then you need Samkey to change CSC to specific one.

 

[Geekser]

I have an s21 ultra and would like to get att wifi calling mine is unlocked tmobile branded with att sim. Would you be able to let me know what steps/files you flashed to get this ?

Thanks alot !

I didn't follow any special steps. I just flashed it in Odin exactly as I described - I put the G998U1 files for BL, CP and AP into Odin and then added the CSC file from the G998U firmware.

In the meantime, I didn't touch my SIM card like others say they did.

I don't mean to confuse the issue, but Subsequent to all of this, the last time I flashed, I simply flashed the entire firmware file for G998U1 - and on reboot after flashing I still had WiFi calling (the only enhanced calling feature I did not have was ATT Video Calling.

 

[cjegan2008]

Hello all, it's been a while since I've done some flashing, used to be a flashaholic lol.

So my question is, if I use the HOMCSC will I retain all my data and have the bloat free U1 firmware or must I flash the regular CSC that wipes the phone to make the U1 firmware changes?

AKA I wanna dirty flash U1 over ATT firmware and not lose all my data.

Thanks in advance!

I wouldn't do a dirty flash on this device. The surefire way to remove all the AT&T bloatware is a clean flash.

 

[cjegan2008]

I have an s21 ultra and would like to get att wifi calling mine is unlocked tmobile branded with att sim. Would you be able to let me know what steps/files you flashed to get this ?

Thanks alot !

You would have to flash this using Odin. I am using the U1 software with AT&T calling working fine, no issues. However, your device has to be on the U1 software without any T-Mobile firmware.

 

[cjegan2008]

Sorry for disturbing. I have question if I flash from AT&T firmware to XAA U1 firmware via Odin will it change CSC or need to change CSC via Samkey? I know for Exynos models if you flash multi csc firmware then you need Samkey to change CSC to specific one.

CSC will be XAA after flashing this. All updates from then on out will be U1 updates directly from Samsung, no carrier bloat.

 

[moobieboobie]

I'm waiting on an ATT version to arrive and plan to flash the unbloated firmware here. My question is, once it's flashed, will the phone receive OTA updates via phone or will a new firmware have to be flashed each time? I haven't been on the forums since the S4, so it's been a while... Thanks

 

[cjegan2008]

I'm waiting on an ATT version to arrive and plan to flash the unbloated firmware here. My question is, once it's flashed, will the phone receive OTA updates via phone or will a new firmware have to be flashed each time? I haven't been on the forums since the S4, so it's been a while... Thanks

It will have the firmware through OTA directly from Samsung, not AT&T.

 

[TheCoryGuy]

There a good source for updated OTA firmwares? SamMobile doesn't have the SM-G998U1 for whatever reason

 

[janeking12]

I used to adore Samsung S21, S21 +, I was an avid android user, never thought of cheating on it. Until it began to turn off the confidentiality mode of the employee monitoring software (connected to my PC), my geolocation, my ads, and my email distribution. When I switched to an iPhone things got better for some reason, . Do you think i should continue with apple or maybe try upgrade something in the android settings

 

[kberger65]

There a good source for updated OTA firmwares? SamMobile doesn't have the SM-G998U1 for whatever reason

Try samloader https://github.com/nlscc/samloader.