Believe it or not, there are still plenty of phones which have not been officially updated to Marshmallow just yet. The BlackBerry Priv is one of those devices, although it worth noting that BlackBerry has made the updated software available to a smaller number of users who are part of the beta for it that they released earlier this year. As of now AT&T BlackBerry Priv owners are able to join in the beta and get access to Android 6.0 Marshmallow software along with the other models that have been enjoying it thus far.
There is one thing to note with AT&T being included in the Android Marshmallow Beta program. AT&T Priv owners will likely have to already be signed up to be part of the beta if they want to receive an invite to the latest build of the beta which appears to be build number 6. Without having already signed up, it's highly unlikely that a BlackBerry Priv on AT&T will end up with an email invite to join in. Having said that, the email invites have reportedly just started making their way out to included users, so it may still be a little while before the email shows up for you if you have previously signed up to be a part of the program. Interestingly enough, if you own the BlackBerry Priv on T-Mobile, the update to Android 6.0 Marshmallow should have been hitting your device as of just earlier this week, and this is an official update.
With the beta now accepting AT&T models of the BlackBerry Priv, the official update may not be far off, although it's important to remember that since the beta just started for the AT&T model of the device, AT&T is not likely to start sending out the OTA update to subscribers this week. Once AT&T BlackBerry Priv users have gotten the update installed on their device, they'll be able to look forward to a number of new features and changes like Now on Tap, more granular permissions control, App Standby, and Doze Mode. Users will need to sign into BlackBerry Beta Zone to be part of the beta discussions, and they'll also likely find useful information about the beta software as well as be able to share their own personal experience with the update.