Although it’s not fully available, you can still download Android 9 Pie final build.
Only a number of handsets are compatible with the preview of Google’s next major operating system upgrade, the Android P Beta.
Downloading Android 9 Pie – It’s pretty straightforward
1. You’ll need to own one of four phones to get the Android Pie update right now. The handsets which can get the update as of today are;
Pixel 2 XL.
2. Android Pie will arrive as an over-the-air update, so you’ll need to head to
Settings > System > System Update to see if it’s landed on your handset.
You may even get a notification alerting you that the Android 9 update is available.
3. Tap download and install.