Deploying rancher/hello-world cannot select port 80

Hi, I am new to Rancher, trying to deploy the rancher/hello-world example with following steps:

  1. Oracle VirtualBox and Ubuntu 20.04 with Rancher docker installed
  2. sudo docker run --privileged -d --restart=unless-stopped -p 80:80 -p 443:443 rancher/rancher
  3. Following tutorial on Rancher Docs: Workload with Ingress Quick Start
  4. At step 9 of “Expose The Application Via An Ingress”, I cannot select port 80 (port 443 is the only available port to select).

How can I proceed? Thanks.