The first HTC smartphone to run Android 6.0 Marshmallow is the One A9, as you may know. But the first HTC handset to be updated to the latest version of Android is in fact the One (M8) Google Play Edition (GPE), the Sense-less version of the Taiwanese company’s flagship for 2014.
Android 6.0 for the M8 GPE has all the same basic features you get on a nexus device like doze mode, granular permissions, and the system UI tuner. It also has the November security patches, which just rolled out to Nexus devices. This might be the last major update the M8 GPE gets. The software is developed by HTC not Google, so it’ll probably move on soon.
The Android 6.0 update for the HTC One (M8) Google Play edition weighs in at around 450MB. If you haven’t received it yet, don’t panic or call the National Guard. The update should be arriving soon. When you do get notification of its arrival, make sure that your battery is charged to at least 50%, and be connected to a Wi-Fi network before downloading and installing the update.