I was able to regain access to a lot of ipsw app backups from old Time Machine drives, in case you are wanting apps that are easy to use on your device. Any files from your backups will work, since they'll have your Apple ID in them.
Can you not install apps from the Purchased section in the App Store? I was able to download the new version of an app on my iOS 18 iPhone, then reload the App Store on iOS 9 and download from the "Purchased" section, assuming the app existed back in the iOS 9 days or had a version targeting this old OS.
Can you not install apps from the Purchased section in the App Store? I was able to download the new version of an app on my iOS 18 iPhone, then reload the App Store on iOS 9 and download from the "Purchased" section, assuming the app existed back in the iOS 9 days or had a version targeting this old OS.