[TazeTSchnitzel]

One way to work around Apple forcing you to upgrade to the latest version is to buy older devices that are no longer supported. The iPhone 7 for example can't be upgraded past iOS 15.

Unfortunately for this strategy, Apple tend to drop support for several devices at once, so there's no device whose final version is iOS 14, for example. With that said, if you're desperate, you could get new-in-box old devices, assuming those devices can still be activated (not all can).