Dealing with Obsolete APIs

I just started Mosh’s “Xamarin.Forms” course and while digging a little deeper to understand the XAML OnPlatform class, which is covered in the XAML Essentials section of the course, I read from the Microsoft documentation (i.e., OnPlatform<T> Class (Xamarin.Forms) | Microsoft Docs) that this class is now obsolete as you can read at the link provided.

My question is where do you look to find an alternative approach or class for solving the problem that is being solved by this class?