By my title you can tell what this is about. I've read practically every article and post I can find and the sentiment is the same. No sense in rehashing the problems. And yes I've tried everything. Only solution is to use Odin and roll back to 11. Absolutely ridiculous.
So happy Android 12 is running nicely on your Z fold. Excessive battery drain is the main problem. You say maybe someone here can help but you then pass the buck over to google...So Samsung is installing untested firmware. Samsung installs Android on their phones so they would be just as responsible for functionality and performance issues as Google. As I stated previously, I've tried everything. Updates shouldn't be released until all bugs are resolved. Browsing through these forums the problems are pretty much all the same and primarily on the S series phones.
It's a conundrum as to why an update can sometimes affect a phone model differently @Dg16_oz
My personal opinion is this can be due to.......
Android 12 is from Google and Samsung One Ui is Samsungs Skin however before Samsung push out these new Google Android updates they make use of in-house Beta Testers and Beta Testers who apply to be part of the Beta Programme and ask those users to send any feedback so that as many bugs can be ironed out as possible before the final release stage.
Phone's do collate broken and unused files along the way which is why one of the generic troubleshooting guides as highlighted by @Glenntech is to clear the phone's System Cache Files.
Another good guide is to use Safe Mode.
The phone's own diagnostic tool under Device Care and Battery can help to highlight potential issues.
Battery drain isn't easy to pin point and is usually broached by a process of elimination by going through everything that can potentially drain the battery ranging from apps, background usage, age of battery, sync schedules ,and even signal strength.
Samsung also provide a feedback process to highlight issues and send error reports via the Samsung Members App under the GetHelp section.
You are quite correct that their are various posts here and elsewhere in relation to Android 12 in that some have experienced various issues, or they don't like some aspects of what Android 12 brings or changes and that can be said by all of the major updates when moving from a current software to the next.
My Fold³ is stable going from Android 11 to 12 however I did experience a glitch from the Samsung Keyboard, however this was resolved by taking the keyboard back to default.
I know from what you write that you have tried everything so maybe the next step is to visit a Samsung Experience Store or Samsung Service Centre so they can run in-house diagnostics.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "