We converted all of the existing talk pages on Officewiki to Flow.
When you create a new talk page on Office, that page should be a Flow board. (We're not going to keep re-running conversion scripts.)
James created a new talk page today, and it's a regular wikitext page:
https://office.wikimedia.org/wiki/Talk:COO/Input_for_discussion_regarding_the_reorg
This is going to be important for T98384: B5. Spike: Namespace conversion for wikitext talk pages -- test conversion on testwiki, make reasonable fixes.