You say you have upgraded all other dependencies but you are still using NgbBootstrap 13.x.x and Bootstrap 4.x.x, these also need to be updated to 17.x.x and 5.3.2 respectively in order to support Angular 18.

The cleanest and easiest way to do this to manually uninstall all NgbBootstrap and Bootstrap packages and then use ng add @ng-bootstrap/ng-bootstrap which should handle the installation of all relevant packages correctly.

If the issue still persists once you have done this then please provide an update (it could potentially be just a missing or renamed icon).