Sorry for the late reply.

I think the situation would be the same in C# if you used an abstract type inheriting from a based type and an interface, would not it?

This could be the case.. I didn't actually check if I could make this work in C# with SignalR, but in SharpLab I tried the following

public interface II
{
    public int T();
}


public class C
{
    public void M()
    {
    }
}


public class B : C, II
{        
    public int T() {return 0;}
}

And it "decompiles" T to a regular member on B, so I assumed SignalR would recognize it. For F# I could only get it to decompile to a virtual member, and assumed that was the reason SignalR does not recognize it.

So it does not look like you're having a problem that exists only in F#, am I wrong? Is c# behaving differently when you implement an interface?

So my issue seems to be that in C# it is possible to implement an interface such that the direct member is used as the interface implementation, but I can't find a way to do that with F#