[throwaway744678]

As said in a sibling comment, you can try it in a desktop browser (Chrome instructions below):

- open developer tools, Toggle device toolbar, pick an iPhone dimension

- Network > More network conditions ("wifi" icon) > User-agent > Custom > "iPhone Safari"

- in Sources, set a breakpoint on the 1st line, refresh the page, when the debugger breaks, type "window.navigator.standalone = true" in the Console, and continue