This sample shows how Application Customizer can be hidden from tenant external users. This is often the ask from the business when a SharePoint Framework App customizer or a web part has internal links that would be broken if a guest user attempts to access any or them.
Open this sample in the gallery (popup panel): Open in gallery
Source: https://github.com/pnp/sp-dev-fx-extensions/tree/main/samples/react-hidefrom-externalusers