Consider I have:-
myapp.firebaseapp.com
with it\'s own manifest.json
.myapp.firebaseapp.co
Old questions, but I want to add to the conversation in case anyone else gets here via Googling - It's possible to remove the start_url completely from your manifest, and the default behavior should be to open your PWA to whatever page the user was on when he saved the app to the device home screen. This ended up being a better solution in my case, ymmv.