springdoc-openapi-gradle-plugin: generateOpenApiDocs fails with Webflux application

I am trying to get the springdoc-openapi-gradle-plugin working with the same Webflux application that is used in the Maven-based springdoc-openapi-demos project.

I run the Spring Boot application successfully, but nothing appears at http://localhost:8080/v3/api-docs.

Similarly, when I run the generateOpenApiDocs Gradle task, I get this:

Timeout occurred while trying to connect to http://localhost:8080/v3/api-docs

My project is available here:

https://github.com/dcp65/springdoc-openapi-gradle-demo

Any idea what I’m doing wrong?