Officially you can’t. Apple stops signing the previous version after the current latest seems stable, or something to that effect. So iOS 15 is way out of reach.
You might be able to Jailbreak your way there but I haven’t done that since my iPhone 4S so I’m pretty out of touch with that world these days.
Kameechewa t1_jafxdlh wrote
Reply to iOS 16 is a nightmare on my iPhone 11. I need to roll back to iOS 15. by Impressive_256
Officially you can’t. Apple stops signing the previous version after the current latest seems stable, or something to that effect. So iOS 15 is way out of reach.
You might be able to Jailbreak your way there but I haven’t done that since my iPhone 4S so I’m pretty out of touch with that world these days.