Older versions of iTunes (like 12.6.5) still have a built-in App Store, allowing you to download apps to your computer.
Perhaps the most magical use for an iOS 9.3.5 device is turning it into a dedicated retro game machine, as you can access thousands of classic games that no longer work on modern iPhones that dropped support for 32-bit apps with iOS 11. ios 9.3.5 compatible apps list
. While most modern apps require iOS 13 or later, you can still use many popular services by downloading "last compatible versions" through your App Store purchase history. Older versions of iTunes (like 12
You cannot usually download a new app directly from the App Store if it requires a newer iOS. To bypass this: ios 9.3.5 compatible apps list