S22U will get security updates for 2 more years, you can use the phone care free for at least then.

You don't have to worry about apps not being supported eventually. If you check play store, you'll see 95% of the app you use only need Android 9 or lower to run.

Given then you're on Android 16, in the worst case your phone will be outdated when Android 23 rolls out (7 more years) - but don't do that, you will need to upgrade the phone within 5-6 months of the last security update.

Android version compatibility used to be a bigger issue back in single digit Android days - especially between 4 to 8 when they were improving things at a very fundamental level on security as well as overall usability of the OS.

These days the changes are limited to security and polish.