Another interesting observation - the iOS 15 intermittent touch screen (where it doesn’t respond to touch) is only ever an issue when navigating around on your phone and scrolling webpages, but it NEVER comes into effect when the keyboard is up and you’re typing (if it did the phone would be unusable, and they’d have lots of unhappy customers in Apple stores complaining)
So that shows it’s software introduced and nothing to do with the actual hardware. Just another one of those things introduced to make the phone ‘feel’ old and slow, like you need to go and buy the latest model, which of course will ‘feel’ smooth and snappy to use in comparison! Thanks again Apple for trying to force an upgrade!