App runner linked custom domain not working when I type www in browser

Hi, You could look in this article https://repost.aws/knowledge-center/redirect-domain-route-53.

The solution typically uses S3 bucket to perform redirection.

Thought working, another approach I tried with my own hands was to use CloudFront functions: https://medium.com/@alatech/domain-redirection-with-cloudfront-functions-32a6732d589d

Depending on traffic and cost appetite, you can decide what is the best approach to redirect from apex to another domain based on above articles.

I hope it helps ;)