It is easily possible to show the Always On Display on Galaxy phones while charging through such option in Settings, but then you lose the ability to show it when tapping the display. Here is a quick tutorial on how to make it show up both ways.
So we have that somewhat useless Bixby button on Galaxy phones. Now I am not against Bixby, quite the opposite. But I prefer to summon her via voice and use the button for something I commonly need to happen fast - turn on the flashlight.
Recently Google started rolling out this new feature to Windows users and apparently it is possible on Android as well. It has been in the Chrome for Android Beta for quite some time. You can follow this tutorial to guide you through the process.