I haven't tried setting it up with https from the container to the load balancer, the load balancer takes care of SSL/TLS termination in my config. Using Route 53 as DNS with an A record using the alias functionality pointing to the ALB.

Any way, the config was not up to date by the way. I have updated the dockerfile and the task definition (some new env variables) in the article now. There was some changes in Keycloak 24. Check if it works with those changes.