AsPocket-lintpoints out, some features new to iOS 15 will function on older devicesjust not everything.
trees, landmarks, etc).
Personalizations for your gadget, like new words, also won’t be available, along with on-gadget dictation.
Apple
Some iOS 15 Features Won't Work on Older iPhone Models
iOS 15 can be installed on iPhones as far back as the 6S, but anything older than an iPhone XS won't be able to access all the new features.
