Starting with iOS 16, iOS devices have had the option for phonetic input of Cantonese. It's a bit of a fuzzy system, allowing for both Jyutping and Yale input, and that makes it accessible to a wide base of users. If you're not quite sure how to enable this extra Cantonese keyboard, then read on below.
First, go to your iOS device's setting and tap "General."
The next screen might look a little different depending on how many keyboards you already have enabled. No matter what your list looks like, head for "Add New Keyboard..." at the bottom.