I emergency disabled Flow on the English and Japanese Wikiversities due to conflicts with their "Topic" namespace and Flow making those pages inaccessible.
As far as I can tell, fawikibooks and dewikivoyage *also* have namespace name conflicts but those pages are not broken...I've left Flow enabled there for now.
Phab bug: https://phabricator.wikimedia.org/T107846
-- Kunal