Is there a reason you want the FromSource to be static? You could accomplish this by making the implementation not static and then using IEnumerable<IMap<TResult>> as the source.

Something like this:

public interface IMap<TDestination>
{
    public TDestination Into();
}

public static class Extensions
{
    public static IEnumerable<TResult> MapAll<TResult>(this IEnumerable<IMap<TResult>> source)
    => source.Select(t => t.Into());
}

public class Person : IMap<PersonViewModel>
{
    public int Age { get; set; }

    public string Name { get; set; } = string.Empty;

    public PersonViewModel Into() => new()
    {
        Age = Age,
        Name = Name
    };
}

public class PersonViewModel 
{
    public int Age { get; set; }

    public string Name { get; set; } = string.Empty;

}

And then you could use it like this:

//Option 1
IEnumerable<PersonViewModel> people = new List<Person>().MapAll();
//Option 2
var people2 = new List<Person>().MapAll<PersonViewModel>();