I have in a single repository, several projects in subdirectories, each corresponding to a different site, this option would be important for me not to need to create several different repositories, each containing a single site.
It can be done, although it’s not at all documented. Two steps: add the domain you want to use as a custom domain in Pages, the normal way to add any domain. point the CNAME to branch-name.[subdomain].pages.dev. It works for me just fine, you might need a little bit of time for the certificate to issue.
