I have a S21 ultra which is still running android 12, UI 4.1 and hasn't had a security update since September 2022. When I check for updates it says its upto date. I've tried through smart switch and that also says its upto date.
Thanks. This is strange, I had expected a mismatch between the carrier and the firmware. Please could you download the Root Checker app from Play Store, run it and let me know the result.
It's a very long thread but I think the CSC was changed by an application which subsequently preventing updates and restoring the original CSC would restore updates.
No, you don't sound thick, it's pretty complicated how they arrived at the conclusion. The solution is to change the csc to O2U. There is a free tool to do this. Check out XDA Developers.