Caught up with some MacWorld reading and it seems the macOS Sierra public beta was released in early July. Want to be a test pilot? Sign up to the Apple Beta Software Program with your Apple ID. You can sign up for both macOS and the iOS.
This public beta software is confidential, so you can’t share any information about it except to send reports directly to Apple with the built-in Feedback Assistant app.
As this is pre-release software, you should not try this on your workhorse mac. Some applications may not be ready for macOS Sierra, but some will have public betas ready, which they hope to recruit feedback for as well.
This sort of exercise has solved many problems I have had over the years with various software so I am glad to see this happening again.
If you have been dying to try out macOS Sierra, want to put it through its paces, want to help iron out conflicts for a smooth ride eventually, and can’t wait for the official release in a couple of months, then sign up here.