I tried the app too a couple of months ago. I tried with Safari and Ecosia.
The browser works better.
I prefer to use Ecosia as a browser. Easy to pin BYC. And most of all they plant trees from the profit.
This is how the shortcut looks on my IPhone screen.
PS i have a iPhone 11 (4-5 years...
I have two iphones, one for my work too.
On my privat phone I use two browsers Safari and Ecosia. On my work phone only Safari. I tried all 3.
On none of them , the install button functions.
I thought it might have to do with regulations in Europe. :idunno
No problem. The website is good...