iOS has excellent accessibility features built in. Take a look at VoiceOver or Zoom [1]. You should be able to toggle either on easily via the Control Center. [1] https://www.apple.com/au/accessibility/iphone/vision/
There is a lot of stuff in the iOS accessibility tools, but unfortunately nothing that makes the text on HN bigger. Ironically, setting the "dynamic text size" makes all kinds of text in the OS way too big but lets the text on HN as small as before. And I don't want to "zoom" because that makes the text overflow the screen on the right.
Or maybe some JS bookmarklet (never tried w/ iOS Safari), personally.
I also thought there was an "Accessibility Zoom" that uses 3-fingers (for all iOS, not specific app)?