Yes, i followed this as i said i have two devices one with iOS 15 and another one with iOS 16. In iOS 15 it is working fine i can see the h3 protocol in response but in iOS 16 it is always h2 for the same domain which gives h3 in iOS 15 and also in iOS 16 i can't see HTTP/3 option to turn on, i can see that option in iOS 15.

Yes, I have followed the above link, i have tested on the device only not the simulator. I have two devices one is running in iOS 16 and another one is on iOS 15 HTTP/3 works fine on iOS 15 but not on iOS 16. The HTTP/3 option in the developer app is missing in iOS 16.