Web apps are a great way to save offline-capable applications without going through an app store. However, the ecosystem behind them is rather convoluted to a normal person, which makes them a bit difficult to install and use. So this is a simple guide to installing web apps on various browsers:
In Chrome, for supported apps, a small “Open in App” button appears on the right side of the URL bar. Click that to download the app.
Safari on all the Apple platforms (iPhone, iPad, macOS) all work fairly similarly: