The UI is not running under AEM domain for localhost, this is only available for Cloud Service instances.Instead of:https://localhost:8443/ui#/aem/universal-editor-canvas/you have to usehttps://experience.adobe.com/#/aem/editor/canvas/ Best,Max

Please see: https://experienceleague.adobe.com/docs/experience-manager-cloud-service/content/implementing/developing/universal-editor/architecture.html?lang=en#building-blocks  Universal Editor consists of two elements: UI & Service.The Universal Editor UI is always hosted on https://experience.adob...

That's maybe something we have to improve the documentation. Actually the 404 is correct and the UES is working on your localhost. Try https://localhost/corslib/LATEST and you will see you will get the latest universal-editor-cors library.