On the 17th of March Windows 10 Mobile (Build 10586.164) was released for existing Windows retail handsets (6 in total) and 18 Windows Phone 8.1 devices that were deemed eligible for the upgrade to Windows 10 Mobile Current Branch (CB).
Since then the Windows 10 Mobile update has filtered out to unlocked devices without much of an issue.
However, those users on AT&T with Windows Phone 8.1 devices such as the Lumia 1520, Lumia 830 and the Lumia 640 (Go Phone) are still waiting in the carrier to release the Windows 10 Mobile CB update for their eligible handsets.
I have two test devices (Lumia 640 (Go Phone) and the Lumia 830) that are both showing, according to the Windows 10 Mobile Upgrade Advisor, as eligible for the upgrade but waiting on its release from my carrier. In this case it is of course AT&T.
I reached out to the mobile carrier to see if I could get a status on the updates release but only received silence in return. A search of their website finds that the last update pushed out was for Windows Phone 8.1 earlier this year.
Several users on Twitter also confirmed they continue to wait for AT&T's release of Windows 10 Mobile but AT&T users are not alone though. I was able to confirm that Verizon customers with the Lumia 735 are also waiting on the update to drop from their wireless carrier for their handsets.
I plan on leaving my two AT&T Lumia devices on Windows Phone 8.1 Update 2 until they finally receive the official update from AT&T.
If you are on one of these eligible devices from any carrier that are waiting on Windows 10 Mobile CB there is an alternative.
You can install the Windows Insider app on those handsets and join the Release Preview Ring which will result in Windows 10 Mobile Build 10586.164, the same build as the CB release, being installed on your device and eligible to receive any future updates that follow for the CB build.
Now, don't get me wrong, this is not how it should work. These carriers need to release Windows 10 Mobile to their eligible handsets so that users have access to it immediately without any workarounds.
Anything less is unsatisfactory, but as we have come to know over the years, par for the course when it comes to the mobile carriers and the pace at which they release updates for their customers.