The entire English Wikiversity namespace has become unreadable with an error message,
Bad title The requested page title was invalid. Pages in the Topic namespace are automatically created by Flow.
See wikiversity:en:Wikiversity:Colloquium#Topic namespace borked
It appears that Flow assumes there is no pre-existing Topic namespace, as Wikiversity has had since being founded.
I hope there is a way to undo this! It's an obvious Flow bug, i.e., the installation should check for a pre-existing namespace conflict.
That bug should be fixed. In the WMF wikis, this may have only affected en.wikiversity, because we may be the only wiki with a Topic namespace, but some other MediaWiki installation might have a conflicting namespace.
The obvious fix is to use an alternate name for the Flow namespace. I checked and it is a translated name on fr.wikiversity, Sujet. So in English it could be Subject. Or Flow!