it’s worth noting that while on android you can be like 4-5 major versions behind and still receive first class app support, on ios apple decides your phone no longer sparks joy and refuses you the next ios version, you’re slowly but surely going to lose all your apps. on the developer side, apple is extremely hostile to the practice of using older versions of their apis, they constantly push you toward newer apis that only work with the latest os and discourage using the older ones. some apps, like vlc, still manage to support older iphones, but it’s an ordeal and a half, so on the user side, not being on the latest ios isn’t really a proper experience.
the iphone 6s was actually the longest supported iphone, receiving the latest ios for 83 months after release. that’s just one month shy of fairphone’s 7 years. however, the average iphone only gets five years of real-world viability*, which is, yes, better than the 2-3 years android gets (usually with way more transparently planned obsolescence than apple does), but it’s not better than the 7 years of true viability that fairphone offers. they upgraded to android 13, that alone would last you until 2026 because of the way android apps are written.