Actually, you can add NodeBB to your home screen already... should work on both Android and iOS.
However we don't show an alert for it because we find it obtrusive... I personally can't stand sites where I have to spend a couple seconds closing the two or three modals or overlays it shoves in my face when I want to read something, and that is reflected in how we don't do any of that in NodeBB.
It's not news to say 2020 has been... challenging. In Toronto, the home of NodeBB HQ, we've gone from a spring lockdown to a cautious summer reopening, to lockdown again — sigh. But the team has never stopped working, and have managed to squeeze out one last release before we thankfully turn over the calendar.