In iOS, it is possible to specify a system-wide desired font size in “Settings > Display & Brightness > Text Size”. Apple calls it “dynamic type” and adding support for it would be a game changer in terms of accessibility.
After discussing it with @bgoncal in this thread, we found that since the iOS App itself is basically a web view, it’d be up to the HA frontend to include the necessary line of CSS.
The change seems pretty simple and is described pretty well in this article:
It describes how support for dynamic type on Apple devices can be added while remaining fully transparent and backward compatible for any non-Apple device. Adding this to the frontend would improve readability not only in the official HA iOS App but also in Safari, should someone use the browser to navigate to the HA frontend.