This seems to be the change, but I can not tell what inspired it:
Update:
For folks in need of an urgent workaround, I was able to use the “New Post” Discourse action in Zapier to trigger notifications to our team’s chat system in lieu of the Discourse chat plugin.
I ended up working around this timed topics bug altogether and triggered the “Zap” based on the time of day, and published it directly to the destination category, so the API will trigger the “New” event and I can use the Discourse Chat Integration plugin to send out appropriate notifications.
It is also possible to watch for topics and then filter out “New topics” (Zapier still sees them as new) that appear in the desired destination category. At first I used this approach but opted for the simpler approach above so I could automate the daily creation of messages to kick off our daily standup.