My mother's upgrading from a Huawei P9 to an iPhone she received as a gift (don't know which model it is).
She doesn't know how to use iOS and I'm finding it difficult to teach her, since I don't know how it works either, so I was wondering if it was possible to install some version of Android on it.
Project sandcastle was always a PoC thing to me. On release, only the iPhone 7 was even close to being able to properly house the OS. Most devices would be missing important things like sound and cellular support, and wouldn't be able to use the camera (among other things, some losing out on more than others depending on the exact device, there's a whole spreadsheet that shows what works and what doesn't for all Sandcastle-compatible devices)
Not to mention, file changes on Android using Sandcastle wouldn't save, essentially meaning every time you reboot it's like a factory reset (your iOS files are fine, just the Android bits wouldn't be saved through a reboot)
There was some fork or continuation of this that brought on a bit more progress since then, but I can't remember the name anymore. No new updates from that one for a while either