A few procedures that I personally find helpful after installing an update are wiping the phone's temporary Cache Partition and using the Galaxy Apps Booster.
Wiping the Cache Partition is considered best practice after a major firmware update and can solve a lot of issues, such as lagging and apps foreclosing. This does not affect your data and is very simple and easy to perform.
Whilst in Recovery mode you can also select the option to, "Repair apps", in case you are experiencing app issues.
This video will show you how to clear your phone's temporary Cache Partition of any corrupt files and detritus that may cause issues for you. It works on all S21 series devices...
To view this video, you must Accept and consent to the use of cookies.
I also use the Galaxy Apps Booster as well, which can be found in the, "Good Guardians", app in the App drawer of Android 12.
(If you do not have Good Guardians in the App drawer, it can be downloaded from the Samsung Store)
Simply run the Galaxy App Booster. If it is your first time using this app it can take awhile to finish. Subsequent runs are around 4 min's.
I downloaded a app from Google play store and then tried to uninstall and it's still on home screen and is sitting in system Apps,I have tried several things for this and I can't even do a factory reset and my Apps keep crashing. I have a Samsung galaxy S21-5G and still under warranty.Any advice please