One of the key differences I noticed between the normal c# SDK and .net core SDK was the Filters collection being 'object' instead of a typed value - is this an intended update or a bug? In the interim I created a class that was similar to the 'NotificationFilterField' object class from the C# SDK for passing this collection.
I also noticed .Filters is null and you need to create the collection first, unlike the C# SDK where it is pre-created.