AT&T just started rolling out Android 6.0.1 Marshmallow update for the Samsung Galaxy S5 Active (G870A) smartphone (a rugged version of Galaxy S5). The update comes with build number G870AUCU2DPH2 and it’s around 906MB in size.
The update brings all the default Marshmallow goodies, including Google Now on Tap, more advanced app permissions, Doze battery sever mode along with Wi-Fi calling, Video calling, and Android security updates.
The update is rolling out through Over-The-Air (OTA) in stages, so it may be take a few days before your device pops up the notification for you. You can always check for the latest update manually by heading to Settings > About device > Software update.