I will share how to downgrade from one ui 4.1 to 3.1 using my s20 fe 5g. This method will work for all the devices.
Points to note:
Sometime this may be brick your device if you don't use the correct flimware. Risk on your own. But if it's under warranty then samsung will solve this problem for free of cost.
It won't void your warranty.
It won't unlock bootloader
It won't trip knox
First check your model number in phone setting
Then check your software name
Check that xxu4 that "u4" may vary with other devices so you have to downlaod the flimware based on that. Mine is u4 I downloaded the u4 named package.
You can download the flimware for free in above link no sign up or payment required
Install Odin any version
Open Odin
Unzip the downloaded flimware
Switch off your phone
Plug it in laptop then press volume up and down button at same time then download mode will open
Your device will appear in Odin
Attach each files with Odin
Attach csc file not home csc file in 4th attachment box
Csc mean full wipe data will be deleted
Home csc mean data, apps will be there but it may cause some issue while boot up or software issues due to os compatibility
Finally press start
If you did all above process correctly then it will start downloading in phone or else it will throw any error.
If you have any issue while doing you can ping here
Thank you
