Hello there!

I’ve read the GitHub Pages custom domain docs and they state:

After you configure a custom domain for a user or organization site, the custom domain will replace the <user>.github.io or <organization>.github.io portion of the URL for any project sites owned by the account that do not have a custom domain configured. For example, if the custom domain for your user site is www.octocat.com , and you have a project site with no custom domain configured that is published from a repository called octo-project , the GitHub Pages site for that repository will be available at www.octocat.com/octo-project .

I have configured an organization-level custom domain by creating a repository with the name organization and by enabling pages and a custom domain custom-subdomain.organization.com for that.

Based on the documentation above I was expecting that from now on all pages that do not specify another custom domain would be found under custom-subdomain.organization.com/repository-name but that is not the case. Instead, I get 404 " The site configured at this address does not contain the requested file. "
What am I missing? Is there any way to enable a custom (sub)domain for an entire organization such that all pages would automatically use that domain as explained in the docs?

Repository-specific custom domains work as intended, but setting up a new one for each repository is not a feasible solution. Redirection from organization.github.io/repo-name also works but that too is not an acceptable solution since it redirects to the default (unusable) domain name that all private pages have (unless a repository-specific custom domain is set).