As of my last update in January 2022, there isn't a standardized way to directly open a specific app on a Windows Phone using a hyperlink (href). The ms-phone:// protocol you mentioned is used to launch the phone application, but it doesn't support targeting specific apps.
However, you might be able to achieve this indirectly by using custom URI schemes if the specific app you're targeting supports them. Here's how you might do it:
1. Check if the app supports URI schemes: Some apps define custom URI schemes that can be used to launch them directly. You would need to consult the documentation for the specific app you're targeting to see if this is possible.
2. Construct the hyperlink: If the app does support custom URI schemes, you can construct a hyperlink using the scheme followed by any parameters required by the app. For example:
html
<a href="myapp://action?parameter=value">Open My App</a>
3. Replace myapp with the custom URI scheme of the app, and action and parameter=value with any specific commands or parameters required by the app.
4. Handle fallback: Since not all users may have the app installed, it's a good idea to provide a fallback option, such as linking to the app's page on the Windows Store or providing instructions for installing the app.
Keep in mind that the availability of custom URI schemes depends entirely on the app developers, and not all apps support this functionality. Additionally, support for Windows Phone has significantly decreased over time, so the options available may be limited compared to other platforms like iOS and Android.
