Looks like HTC has kept to their promise of delivering Android 6.0 Marshmallow update to its slew of flagship devices, which will also include the once mighty HTC One (M8). After all, it has been reliably reported that the Android 6.0 Marshmallow update has begun to seed Over The Air (OTA) for folks who are rocking to Verizon and T-Mobile carrier versions of the device.
Verizon-backed owners will be on the receiving end of a software version 6.21.605.3 package, whereas those who are subscribed to the Uncarrier will see their software version get bumped to 6.20.531.5. It does not matter, really, as both of them will be based on Android 6.0 Marshmallow, which will see a slew of experiences that are exclusive to Marshmallow including Dozing, run time permissions and the like. Not only that, one should also be able to check out new volume controls for notifications, audio and alarms as well as a more simple screen capture process.
Do take into consideration that regardless of whether you are with Verizon or T-Mobile, both of these carriers will conduct a staged roll out, so some patience would come in good order. After all, have we not heard it a million times before that good things come to those who wait?