Listen to Radzen Blazor component rendering completed

How can I have a component get notified when a nested Radzen Blazor component is rendered?
In the parent component I have:


The JS code:


It works only after subsequent reloads from the browser. At the initial load I get an error saying that the button that I target is null. That is understandable, the code fires before the Radzen SplitButton component has been rendered.

If I define a component inheriting from SplitButton and override OnAfterRenderAsync there maybe this could solve it?