Does anyone know how apple prefers to receive feedback on macOS Sierra? Do they want feedback prior to beta release? There is a feedback app., but it only lists El Capitan and iOS 9...
How does apple want feedback?
At this early stage, scroll down to the bottom of these web pages, and next to Contact Us you should see Report Bugs, is another way if the "feedback app." is not working correctly.
When I last checked, Feedback Assistant was for AppleSeed projects and public betas; and developers should (as indicated by xplora) use Apple Bug Reporter.