Downgrade from OneUI 3 to 2

[RedP]

I have a Galaxy S20 UW on Xfinity Mobile that just updated to One UI 3 / Android 11.

The upgrade has absolutely destroyed the split screen / multitasking capabilities. I've had the firmware flashed by a Samsung Care person, and he told me reversion is impossible, but intense googling says that user @CHMultimedia might be able to help.

Baseband version G981VSQU1CTKH

tia

[Halston]

Hi RedP,
It is not possible to downgrade from one version to the previous version once it is updated. Please note that the flashing of the device may cause misbehavior of the device and it voids the Samsung warranty. Samsung always recommends to keep the device up to date to get a better experience.
I suggest you to perform the wipe cache partition of the device and get back to us with the results. You can also attach some screenshots of the issue split-screen / multitasking capabilities.
Please follow the steps below to perform the wipe cache partition.
1. Turn off the device.
2. Press and hold the Volume Up key and the Bixby / Power key.
3. When the Android logo displays, release both keys.
4. An 'Installing system update' message may show briefly before the Android Recovery menu options appear.
5. Press the Volume down key several times to highlight Wipe cache partition.
6. Press Bixby / Power key to select.
7. Press the Volume down key to highlight Yes, then press the Bixby / Power key to select.
8. When the process is complete, reboot system now is highlighted.
9. Press the Bixby / Power key to restart the device.

[RedDogRabbit]

That's false! Flashing the stock Samsung firmware with Samsung's Odin tool does not void the warranty, it's not rooting the phone & it doesn't trip knox warning, there's no trace that anything has been flashed. 

Having said that, the only time that you can't flash back to a previous version is if there's been a bootloader update. 

[RedP]

Dude, go away. Nobody needs your tier one script. The split screen issue is a known issue, there are threads going back months and the devs just don't care.

And seriously? You're going to try to tell me that a Samsung Care expert "voided my warranty"? Just shove off.

[oooOmitoOooo]

That dude is a mod and he won't go away.

:)

[RedDogRabbit]

Well, if he's a moderator he should know what he's talking about, instead of providing false information. 

Samsung's moderators seem to suggest wiping cache as a solution for everything, sure sometimes it can help, but suggesting that wiping cache will miraculously update Good Lock modules for one ui V3.0, when there's no updates available until next year...

@RedP is right about "tier one support". 

[RedP]

You want to be helpful? Ask @CHMultimedia to join the chat.

[CHMultimedia]

Hi there! You're lucky I still glance at this forum from time to time in a foolish attempt to see if things improved here, and also that I'm currently on break from college. I've had to stop helping people in the European forums too due to a sudden increase in work so...

Anyway, I'm currently uploading everything you'll need to revert to Android 10 Q. Whoever told you rolling back is impossible isn't the slightest concerned about actually helping you with factual information. All he did was reflashing the latest, bugged release. As RedDogRabbit mentioned so accurately, you can freely revert back to any firmware, as long as the Bootloader fuse wasn't incremented. And lucky for you, you are still on v1 of the fuse (it's the 1 besides the C in the baseband version).

Expect the "Everything you need to have a functional glass slab" kit very soon

And yes, it's 100% genuine, untampered Samsung firmware. In North America, you can't void your warranty by flashing even if you wanted to, since the bootloaders are not unlocked. You literally can't flash non-genuine firmware, your phone won't accept it.
Oh and @Tagging doesn't work here sadly

[CHMultimedia]

Start with downloading THIS on your computer.

While it's downloading, you may consider backing up your data. It shouldn't wipe your phone but better safe than sorry.

Okay, next you should open the Odin executable. Click on the button labelled "AP" and in the window that appears, select the among the files you have downloaded the one whose name starts with AP. See the first image. Click on the buttons in Odin and feed it with the corresponding file.

Repeat with "BL" and "CP" (select the file that starts with BL and CP accordingly).

For "CSC" select the file that starts with HOME_CSC.

The next step is to turn off your phone and then hold the Power+Volume Down buttons for a few seconds. See the second image.

You will see a teal warning screen. Don't worry about it and select Volume Up to continue. Now your phone is in Download mode. Plug it to your computer.

Now all that's left is to hit Start on Odin. Wait a while and you should be back on Android Q

[RedP]

You're a god among men. The Samsung Care guy did really try, in his defense. He was only going to take my money if he was successful and he wasn't.

I'll let you know how it goes.