I want to track when the popup element of the DropDownButton is opened and closed.

===

ADMIN EDIT

===

For the time being, a possible option is to use the DropDownList component that exposes such events. Customize it so it can look and behave similarly to the DropDownButton.

Example implementation: https://blazorrepl.telerik.com/mekbkTPE21kwyMBU05.

By default, the dropdown popup is automatically positioned 100% from the top and along the left side of its parent (the input). I want to customize this behavior, for example, aligned to the right side of its parent.

For the time being, a possible custom approach is to use a TextBox or Button component as an anchor and a configured Popup component. For example, refer to this REPL link.