How to redirect http errors response? - Custom Error Page

I am working on a web app with springboot, I want to be able to redirect the user when requesting a page that doesn't exist.

I've tried following this guide :https://www.baeldung.com/spring-boot-custom-error-page

But it's not working as expected, the "/error" page works, but If I try to access a path that doesn't exists I get the usual message:

{"type":"about:blank","title":"Not Found","status":404,"detail":"No static resource randomURL.","instance":"/randomURL"}

I would like to get either my custom "404.html" or be redirected to the main page!

First, please confirm that you have added thymeleaf to your pom.xml like this:

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>

Then, ensure that you have added the corresponding HTML files as described at https://www.baeldung.com/spring-boot-custom-error-page, like this:

Lastly, you only need to add a custom controller and implement ErrorController like this:

@Controller
public class CustomErrorController implements ErrorController {

    @RequestMapping("/error")
    public String handleError(HttpServletRequest request) {
        Object status = request.getAttribute(RequestDispatcher.ERROR_STATUS_CODE);
        if (status != null) {
            int statusCode = Integer.parseInt(status.toString());
            if (statusCode == HttpStatus.NOT_FOUND.value()) {
                return "404";
            } else if (statusCode == HttpStatus.INTERNAL_SERVER_ERROR.value()) {
                return "500";
            }
        }
        return "error";
    }
}