.NET Core custom error pages
In Sitefinity .NET Core Renderer, you can handle only 404 custom error pages.
Sitefinity .NET Core Renderer runs in a separate process and all the errors that occur on the separate process must be handled within it. Therefore, the Renderer supports only 404 pages.
This is not the case for MVC and WebForms pages, because the execution of these pages happens within the main CMS process.
For more information about configuring custom 404 pages, see Custom error pages.
For more information about handling any errors in the Renderer process, see Microsoft official documentation » Handle errors in ASP.NET Core.