We host a relatively large self-managed GitLab instance for Bavarian universities (see Introduction: Arto Teräs / LRZ) and are currently running GitLab 13.12.
Our GitLab Pages use a subdomain of the Gitlab instance itself and are hosted on the same servers (a small cluster configuration).
When preparing the upgrade to upcoming GitLab 14.0 I noticed that accordings to the GitLab Pages documentation this kind of domain configuration is not officially supported (GitLab Pages administration | GitLab). When looking back at the documentation of earlier versions it doesn’t seem to be a recent change - just mentioned more prominently in the documentation than before.
It would be a significant inconvenience for our users if we need to change the pages domain. Quite a few have published course information, documentation, results or datasets of their research projects using the current domain. Obviously changing the domain of the instance itself would be a pain as well.
Could someone please explain why Pages on a subdomain of the GitLab instance is not supported? On our instance it has been working already for a couple of years. Should I expect it to break when upgrading to GitLab 14.0? If yes, are there workarounds to prevent that?