How can I show custom error messages using Thymeleaf?

I'm trying to do CRUD operations with Spring. I'm using HTML and Thymeleaf on the frontend. I return the results of certain actions I have made and error messages, if any, using a custom class that I write. I don't have any problems so far. However, if an error occurs during these operations and I return this error through the class I wrote, I do not know how to display it on HTML using Thymeleaf.

I'm returning an object of this class type;

@Getter
@Setter
public class WarehouseAPIResponseHolder<T> {

    private T responseData;
    private HttpStatus httpStatus;
    private WarehouseAPIResponseError error;

    public WarehouseAPIResponseHolder(HttpStatus httpStatus) {
        this.httpStatus = httpStatus;
    }

    public WarehouseAPIResponseHolder(T responseData, HttpStatus httpStatus) {
        this.responseData = responseData;
        this.httpStatus = httpStatus;
    }

    public WarehouseAPIResponseHolder(HttpStatus httpStatus,
                                      WarehouseAPIResponseError error) {
        this.httpStatus = httpStatus;
        this.error = error;
    }

}

My error class;

@Getter
@Builder
public class WarehouseAPIResponseError {

    private String code;
    private String message;

}

Example of an error;

if (CollectionUtils.isEmpty(warehouseEntities)) {
            return new WarehouseAPIResponseHolder<>(HttpStatus.NOT_FOUND, WarehouseAPIResponseError
                    .builder()
                    .code("DATA_NOT_FOUND")
                    .message("No records found in the database.")
                    .build());
        }

The method in my controller class;

@GetMapping
    public String getAllWarehouses(Model model) {
        model.addAttribute("listOfWarehouses",warehouseCRUDService.list().getResponseData());
        return "warehouses";
    }

My HTML code;

<div class="container my-2">
    <h1 align="center">Warehouse List</h1>
    <table>
        <thead>
        <tr>
            <th>ID</th>
            <th>Code</th>
            <th>Name</th>
            <th>Status</th>
        </tr>
        </thead>
        <tbody>
        <tr th:each="warehouse : ${listOfWarehouses}">
            <td th:text="${warehouse.id}"></td>
            <td th:text="${warehouse.code}"></td>
            <td th:text="${warehouse.name}"></td>
            <td th:text="${warehouse.status}"></td>
        </tr>
        </tbody>
    </table>
</div>

I am successfully listing, but if there is an error message I don't know how to display it. I did not use Spring validation methods. Is there any way I can do this in a simple way?