The HTC Desire Eye users (via HTC Blog Italia) in Europe as well as users on AT&T will start receiving the over-the-air (OTA) update next week. The HTC One (E8) is currently only receiving the OTA Marshmallow update in China. The HTC One (M8 Eye) users in Europe and China are reporting about the new update for the handset.
Unfortunately, there is no official changelog for the new Marshmallow updates for the HTC Desire Eye, HTC One (E8), and HTC One (M8 Eye) smartphones. For now, the update is available to limited regions but we can expect it to be available to wider users in coming weeks. Users can manually check for the update via Settings> About Phone> System Update. The Marshmallow update will bump the software as well as bring the new Sense 7 UI.
To refresh, Android 6.0 Marshmallow (previously just Android M) brings features such as revamped app permissions; Google Now on Tap feature; Android Pay mobile payment system, and new fingerprint APIs for developers among others.
The Taiwanese handset maker has so far released the Android 6.0 Marshmallow updates for its HTC One M9 and the unlocked version of the HTC One (M8) also received update in the US. The HTC One A9 received Android 6.0.1 Marshmallow update which brought several bug fixes and the latest set of emojis from Unicode 7 and Unicode 8.