YubiKey’s now work with the iPhone: Buy one here:
You can use a YubiKey 5 series security key to secure your online accounts on Android and on iPhone. The YubiKey 5Ci has a Lightning connector and USB-C, so it is great for using with an iPhone, an iPad or a laptop.
Get a YubiKey:
Introduction to Android app development:
Let Me Explain T-shirt: