Pages with "Unique Domain" misses an API to get the baseurl
When using GitLab pages from GitLab.com (at least, but I guess it's the same for self-hosted), the deploy job has no log. So we cannot know the target base URL. Without "Use Unique Domain" flag, we can at least build it from known structure (although not defined anywhere). With the flag, we can't.
Scribouilli project (https://atelier.scribouilli.org/, https://github.com/Scribouilli/scribouilli/), which is a wrapper around pages (adding one more step to ease deploying a site), can create a pages project, but cannot get the baseUrl to set in config for Jekyll. It is not even available as a CI variable.