Use Dynamic Data as WPF's CompositeCollection alternative in AvaloniaUI

Question

I want to use Dynamic Data as WPF's CompositeCollection alternative in an AvaloniaUI project.

Here is some code to expose the issue :

public class MainWindowViewModel : ViewModelBase
{
    private readonly ReadOnlyObservableCollection<ViewModelBase> _testBind;
    public ReadOnlyObservableCollection<ViewModelBase> TestBind => _testBind;
    
    public IObservable<IChangeSet<ViewModelBase>> SeveralListTypes { get; set; }
    
    public IObservable<IChangeSet<ViewModelBase>> SeveralListTypes2 { get; set; }
    public IObservable<IChangeSet<ViewModelBase>> SeveralListTypes3 { get; set; }

    public ObservableCollection<ViewModelBase> ListTypesObject1 { get; set; } 
    public ObservableCollection<ViewModelBase> ListTypesObject2 { get; set; }
    public ObservableCollection<ViewModelBase> ListTypesObject3 { get; set; }
    public IObservable<IChangeSet<ViewModelBase>> InBoth { get; set; }
    
    
    private readonly ReadOnlyObservableCollection<ViewModelBase> _testBindTypes;
    public ReadOnlyObservableCollection<ViewModelBase> TestBindTypes => _testBindTypes;
    public MainWindowViewModel()
    {

        // TODO : those object collections should be of the real type and not from ancestor
        // ListTypesObject1 = new ObservableCollection<Object1>()

        ListTypesObject1 = new ObservableCollection<ViewModelBase>()
        {
            new Object1(),
        };
        
        ListTypesObject2 = new ObservableCollection<ViewModelBase>()
        {
            new Object2(),
        };
        
        ListTypesObject3 = new ObservableCollection<ViewModelBase>()
        {
            new Object3(),
        };


        // Change observableCollection to IObservable to be running with engine ReactiveUI
        SeveralListTypes = ListTypesObject1.ToObservableChangeSet();
        SeveralListTypes2 = ListTypesObject2.ToObservableChangeSet();
        SeveralListTypes3 = ListTypesObject3.ToObservableChangeSet();
        
        //Group All Observable into one with Or operator 
        InBoth = SeveralListTypes.Or(SeveralListTypes2).Or(SeveralListTypes3);

        // Bind => output to Binded Property for xaml
        // Subscribe => to be notified when changes
        var t = InBoth.Bind(out _testBindTypes)
            .DisposeMany()
            .Subscribe();
    }
    
    public void AddObject1()
    {
        var obj1 = new Object1("Added Object 1");
        ListTypesObject1.Add(obj1);
    }
    public void AddObject2()
    {
        var obj2 = new Object2("Added Object 2");
        ListTypesObject2.Add(obj2);
    }
    public void AddObject3()
    {
        if (ListTypesObject3 == null)
            return;
        var obj3 = new Object3("Added Object 3");
        ListTypesObject3.Add(obj3);
    }

    public void DeleteObject1()
    {
        if(ListTypesObject1 != null && ListTypesObject1.Count > 0)
            ListTypesObject1.RemoveAt(0);
    }
    public void DeleteObject2()
    {
        if (ListTypesObject2 != null && ListTypesObject2.Count > 0)
            ListTypesObject2.RemoveAt(0);
    }
    public void DeleteObject3()
    {
        if (ListTypesObject3 != null && ListTypesObject3.Count > 0)
            ListTypesObject3.RemoveAt(0);
    }
    
    public void DeleteObjectClear()
    {
        if (ListTypesObject3 == null)
            return;
        ListTypesObject3.Clear();
        ListTypesObject3 = null;
        ListTypesObject3 = new ObservableCollection<ViewModelBase>()
        {
            new Object3("Added object 3 from new list 3"),
        };
        SeveralListTypes3 = ListTypesObject3.ToObservableChangeSet();
        InBoth = InBoth.Or(SeveralListTypes3);
        // TODO : the collection we want to remove is still binded, the new one is not

    }

    public void DeleteObject3List()
    {
        if (ListTypesObject3 == null)
            return;
        ListTypesObject3.Clear();
        ListTypesObject3 = null;
        // TODO : remove the Object3List from DynamicData
    }

    public void CreateObject3List()
    {
        if (ListTypesObject3 != null)
            return;
        ListTypesObject3 = new ObservableCollection<ViewModelBase>()
        {
            new Object3("Added object 3 from new list 3"),
        };
        SeveralListTypes3 = ListTypesObject3.ToObservableChangeSet();
        InBoth = InBoth.Or(SeveralListTypes3);
        // TODO : the collection we want to remove is still binded, the new one is not

    }

}

Object1,Object2 and Object3 are an heritage from ViewModelBase.

DeleteObjectClear method remove all Object3 from the binding but then the new list isn't displayed.

How to add or remove an ObservableCollection and refresh the binded object (TestBind) ?

As a second issue, is it possible to use the real type of object in ObservableCollection (with a common ancestor) instead of ViewModelBase and still use Dynamic Data to agregate all collections ?

Here is the full github repository POC to spotlight the issue : https://github.com/Whiletru3/pocbindingdmo

Thanks