Many devices running the android TV OS have options to control the TV volume (or sound system volume) directly, either through CEC or by setting the IR code for the respective device's volume (and power) control(s).
For example, ccwgtv does this, but ccwgtv also has an option to control the android TV OS system volume directly (the volume slider within the android TV OS) by choosing "chromecast" as the "change volume setting" option. Likewise for the walmart onn (askey) android tv box device (which is good because the onn has a low default system volume setting).
But some devices have no "change volume setting" anywhere within settings (tvsettings.apk), or have the option disabled, so there is no way to change the volume control setting to be that of controlling the android TV OS system volume directly, rather than controlling volume only on some external hardware.
My question; Is there some command or way to change this "change volume setting" either using adb or via shell (root or not) so that volume control will return to the android TV OS system volume control rather than though some external hardware's volume control? Not just change the level, but activate the volume slider so that the android TV OS system volume control can be used directly.
My experience is that when the device doesn't have a volume rocker, the system OS volume is 100% like it was on the Nexus Player. If there is a rocker, you can change the system volume similarly to how the Onn 4K does it, but each box or TV has their own menus so you just have to figure it out on a case by case basis.