The Calcite Design System's Calcite Shell React component does not render subcomponents in the Document Object Model (DOM) compared to a non-React Calcite Shell component.
It is not possible to replicate the React calcite-shell component not rendering.
In the example provided, both the HTML and React calcite-shell components are rendered, but one covers the other. If position: relative is added to the #root declaration block, both become visible on the screen at the same time.