Android and free OS based on Android/Linux.
I.e.: GrapheneOS (https://grapheneos.org/) or LineageOS (https://lineageos.org/) for mobile devices
Discussion
by and large android is not an alternative to the iPhone and are not much different. at least there's not a significant difference.
I've been using an iPhone all my life and I don't see it as a worthy replacement either in terms of quality or user experience. sadly