SilverStripe 4.0.0 alpha7 has been released!
In addition to many critical bug fixes and UI polish, this release includes some exciting new features including a brand new, React-based TreeDropdownField, and new Date/Datetime fields that have been rebuilt with HTML5 datetime support.
To get setup, you can install this using composer (as below):
composer create-project silverstripe/installer ./ss40 4.0.0-alpha7