Right now add to home screen popup it appears only if certain conditions are meet.
Popup are in general hated by users, especially if they happen when they do not expect it.
I think we should provide more options how we want handle the UX to install the web app.
I think google app provide a good example of how to install an app.
When you land on the page you see a panel with the app, when you click on the panel
this screen will appear asking you if you wish to install the app
I think we can take inspiration from that example and make it even better. My suggestion is to have a native install button.
The button could have the browser branding like google play does
The button cannot be customise you cannot apply any css or js.
When you click on the button it open a popup of confirmation asking if you are sure to install the web app. Even if it is a button you can still apply limitation on the use to avoid is abused.