My usecase demands that I show a Window when requested by user's Right-Mouse-Click, while current solution forces me to use a Flyout instead. I could use a Flyout with a single menuitem that invokes my window but users don't like that.
A Workaround is to define an (empty) Dummy-Flyout and set the Handled Flag in the Eventhandler in order to suppress the Flyout.ShowAt().

Movement of 1 statement would provide what I need:

The Flyout parameter in the FlyoutEventArgs obviously needs to be nullable then.
Btw. same applies to ShowCellContext().