AT&T customers holding onto HTC's 2015 flagship should be happy to hear that the carrier's page for the phone has been changed with the details of an update to Android 7.0 Nougat, including instructions on how to pull down the OTA. Although we haven't seen any first-hand reports for the update on any devices yet, the mention of the OTA on the page would seem to imply that it should appear soon.
If you don't remember the phone, our review of the M9 found it to be just like the M8, but perhaps slightly more so. (That's a joke and I think it's funny.) The Sprint version of the device got Nougat just a few days ago. It's not too surprising, then, that AT&T would be next up with some Nougat love. It's no small step up from Marshmallow, although unfortunately, the changelog at AT&T's site says it only includes security patches up to February, which is a bit dated.
The relevant instructions for pulling down the update (if it is available) are below:
You can download the update via Firmware Over the Air (FOTA).
You must connect your device to Wi-Fi to download the update.
Although there should be no impacts to settings or data, we recommend that you back up your media files to an SD card, a PC, or using a favorite application (from the Play Store), prior to upgrading the software.
In order to receive this software update, your device must be on software version 3.38.502.41. If not, repeat the update process below until you’ve installed version 3.38.502.41, and then you can install the most recent software update.
To update the software
Make sure your device is fully charged and connected to Wi-Fi.
From the device home screen, swipe down from the top of the screen and tap Settings.
Tap General > About phone > Software updates.
Follow the on-screen prompts to download and install the update.
The device automatically restarts once the new software successfully installs.