My iMac 2020 failed installation over beta7. Downloaded and rebooted then required disk passcode, then went to recovery mode and reboot to beta7.

The Notification should be posted from main thread, if your post is post from escaping closure or other asynchronous ways, the warning will show up. to avoid this, you can post the noti from main thread as: DispatchQueue.main.async {                    NotificationCenter.default.post() } hope could help.                 

The Notification should be posted from main thread, if your post is post from escaping closure or other asynchronous ways, the warning will show up. to avoid this, you can post the noti from main thread as: DispatchQueue.main.async {                    NotificationCenter.default.post() } hope could help.