(C# / Unity) pass generic type into Interface extension

Question

I'm trying to create an interface to handle different types of input where one input class (InputValue) cannot be modified and the other (GenericInputValue<T>) can have different value types

essentially I need to pass the GenericInputValue<T> as the type for IInputHandler<T> (note: not the same <T>)

refer to this line in the code below:

public class JoystickInputHandler : MonoBehaviour, IInputHandler<GenericInputValue<???>>

what do i replace the ??? with?

public interface IInputHandler<in T>
{
    void OnMove(T value);
    void OnButton(T value);
}

// handles standard `InputValue` from Unity Input System
public class NormalInputHandler : MonoBehaviour : IInputHandler<InputValue>
{
    public void OnMove(InputValue value) {}
    public void OnButton(InputValue value) {}
}

// handles generic input values with different types
public class JoystickInputHandler : MonoBehaviour, IInputHandler<GenericInputValue<???>>
{
    // note: each method has a different value type
    public void OnMove(GenericInputValue<Vector2> value) {}
    public void OnButton(GenericInputValue<bool> value) {}
}

// stores a generic data value without object boxing
public class GenericInputValue<T>()
{
    private T value;
    public GenericInputValue(T value) { this.value = value };
    public T get() { return this.value; }
} 

if I can only use IInputHandler<GenericInputValue> then GenericInputValue will need to box/unbox an object to store different types of data, which I'm trying to avoid eg

public class GenericInputValue
{
    private object value;
    public GenericInputValue(object value) { this.value = value; }
    public T Get<T>() { return (T)this.value; }
}

thanks