So for true low-level control on vintage hardware, iOS 9.3.5 + iFile + IPAs is still the king. Is it worth the hassle? If you have an old iPhone 4s collecting dust, yes. Spend an afternoon jailbreaking it with Phoenix, installing iFile, and hunting down rare IPAs. You’ll learn more about iOS internals than any modern “allow paste from” popup could teach you.
But for the tinkerers, the archivists, and the nostalgics: Enjoy the ride. Would you like a step-by-step guide for jailbreaking iOS 9.3.5 and installing iFile? ifile ipa ios 9.3.5
If you want a daily driver? Absolutely not. Stick to iOS 15+. So for true low-level control on vintage hardware, iOS 9