Solved this by putting the link to the webpage in notepad, then doing the following:
- Open MyApp and navigate to the page I need.
- Open Notepad app (which doesn’t kill MyApp when it opens the way the browser does) and tap the link in the notepad that opens the browser page I need.
- Browser opens and I can scroll to the deep link URL needed, tap it, and it opens in the existing instance of MyApp.
A little convoluted, but it works.