Oh, es muss wahrscheinlich nur der site-Dienst manuell importiert werden.
import { apiInitializer } from "discourse/lib/api";
export default apiInitializer("1.8.0", (api) => {
const site = api.container.lookup("service:site");
api.renderInOutlet(
"composer-after-save-or-cancel",
<>
{{#if site.mobileView}}
Mobile!
{{else}}
Normal!
{{/if}}
</>
);
});