Convert UnityEngine.Component to T

That's not really how generics work. The T in a generic is filled in when you call a function or instantiate a class.

  public class myClass<T>
 {
       public List<T> someList = new List<T>();
 }

Then later

  var anObject = new myClass<string>();
 anObject.someList.Add("Hello world");

 var anotherOther = new myClass<int>();
 anotherObject.someList.Add(100);

The List has been created from the generic parameters when I constructed the class.

Perhaps edit the question if your problem is actually something different....