I have an S23 FE. I have no problems. I presume you have searched for it through going to Settings and then searched for either brightness or adaptive brightness. Note on the drop down menu you can add additional buttons. A quick search on how to add buttons will help. I presume when looking at the dropdown buttons you have swiped left to see additional buttons.
Yes, it appeared several days ago, or I may have searched fo it under Settings, scroll to Software. I have two devices so I foget. Under Software there is no obvious link, you just click on the top option and it goes away and checks. If you want to check whether it has been done automatically because of your settings, unlikely, go to Settings, scroll to About and explore under Status
Is there any way to restore the brightness adjustment for Always On Display? This has been removed withe the upgrade. I spent an hour chatting with Samsung chat person last night and she said the same as you but the clock display is still dim whilst everything else is full brightness.
