Have you tried turning "Scene Optimizer" OFF in camera settings? Also, make sure the filters wand isn't inadvertently turned on and applying a filter you're not aware of? I'm also assuming you're using the standard camera app, not Expert RAW or Pro modes.
So it is the refining photo notification which appears 1-2 seconds after a picture is taken - which I am guessing is the processing that you are referring to. The problem is, is that during this processing the pictures appear to get a lot darker and shadowy even, some of them just look hazy and this is only after the "refining" notification appears - the few seconds before this starts happening the picture looks really good. I understand that the phone has to optimise but I don't know why the AI changes the light and contrast so much - I never had these issues with the S21 and the 64 mp camera which is why I can't understand what is happening now.
Useful info re portrait mode though - I will give that a go next time.
I have had it with this phone for that reason too. 200 and 50 mp have auto ai refining that ruins the photo. There's not any current setting that can fix it either. Scene optimizer isn't a fix. Neither is hdr or any camera assistant setting. I have done all the adjustments that I've seen suggested and none work. I find it hard to believe Samsung hasn't had enough complaints to make a way to turn off the ai refinement, but apparently not.