This is applicable for all the Android smartphones.
I have noticed that many people do not Factory Reset their phones when new OS update is done. And then they keep facing a lot of issues
I can understand this can be a dangerous process (if you do not take backup) but if done correctly, this might fix 99.99% (even 100%) of your smartphone issues.
It is always recommended (at least for Android smartphones) to Factory Reset (after taking backup) when a major OS upgrade takes place.
This flushes out all the previous OS's cache, data, app packages that shipped with the older OS. It brings your smartphone to it's initial state (kind of like buying a new phone).
This definitely fixes a majority of issues and bugs that the older OS may have left behind.
You do not need to Factory Reset after regular software updates (unless some major bug is occurring) but better to Factory Reset after OS change.
I've been using my Galaxy Note 8 since 3.5 years now (will complete 4 years in October 2021) and have not faced any issues because I always Factory Reset after OS change (I usually Factory Reset my phone after every 6 months or so to get rid of unwanted data to have a smooth, 'clean' experience).
Same was the case with my previous device - Galaxy Note 4 and prior to that - Galaxy Note 2.
It is like a cleansing process that is good for your smartphone. Depending on your experience, you will need to dedicate one full day for this (as you will need to restore the backed up data, update apps, etc.)
Thankfully, Samsung Smart Switch app makes things quite easy than it used to be in old days.
Backup contacts, messages, apps, settings, even Home Screen layout using Smart Switch.
In addition to Smart Switch, just keep .csv file backup of Contacts on your memory card or laptop as well (as Contacts are most important). Do this via your Phone app settings -> Import/Export Contacts -> Export to SD card.
Take WhatsApp chat backup at the last moment just before Factory Reset so you can restore the chats as well till last time. And store the backup file on your PC / memory card (nowadays it backs up on Google Drive, so no issues).
If you are really facing slowness issues or any other issues on your smartphone, especially after major OS update, Factory Reset is bound to fix all the issues.
This comes from my own experience.
Hope this helps some of you who are facing issues on your phone after recent OS update and no other solution works.
Thank you!
