Unable to use third-party icon packs to change icon appearance in Android 6.0 and higher
In Android™ 6.0 and higher, there is a Home screen setting called Icon appearance. You can choose to apply a different appearance to the icons on your Home screen from an icon pack or a theme. However, this support has to be added by the third-party icon pack developers. Some icon packs already support this setting, and over time, more icon packs will become compatible with the latest Android™ version.