Samsung is rolling out One UI 6 to most of their android phones released in past 3-4 years. But, not all are happy with the latest version of One UI and some even want to downgrade to One UI 5.
Unfortunately, it is not going to be as easy as uninstalling an application from your Samsung android phone.
That said, you can find your phone’s older firmware on Samfm. Make sure to download the one that is marked with same BIT as your Samsung phone’s current firmware. If you do not download the ROM with same BIT, you can potentially brick your phone.
Then, make use of ODIN to downgrade to previous firmware.
Will flashing older firmware void your warranty? No, since you are flashing official ROM that is not tempered anyway. One user was able to downgrade from One UI 6 to UI5 by flashing from BXXS3BWK5 to BXXS3AWF7 without an issue. Both of these firmwares have same binary 3 so the flashing went fine and did not even void the warranty.