Is this forum the best place for bug report?

I expected it might be "Issues" on the github repo, but that shows 0 open, 0 closed suggesting it does not get used.

OK, no answer so went ahead and opened an issue on the github repo. Bug is minor... if you leave the date widget blank when you submit a Announcement, you get put back into the edit page with a validation error, but clicking in the date field to fix the issue does not reopen the date widget. (And FWIW IMO a blank publish_at date probably ought to mean "now", not a validation error.)