Angular language service in VSCode does not work because it is not an Angular project (‘@angular/core/core.d.ts’ could not be found)

Update to @Begandroide’s answer. “Ivy” is no longer considered experimental, and so the Enable-experimental-ivy-prompt is no longer an option. With the latest major version (12.x…) of the Angular Language Service VSCode extension, you must enable the Use legacy View Engine language service option.