I just went from 14 to 15.4
Haven’t seen posted anywhere but iPhones with A12 chip or above can get voice inputs processed on phone.
I find it faster and some voice inputs can be done without an internet connection, even “turn on wifi” or “turn on mobile data”
It understood everything I said even though on US English. It took up to 18 hours on WiFi before it started working. Just made mistake of switching back to NZ English (to confirm if language essential) and it stopped working offline. Switched back to US English, Siri and search has downloading again after it, so hopefully will be back in business in another 18 hours. ( Don’t know why download so slow)