Availability needs to be user-controllable, not only automatic.
Currently (August 2019) Teams decides when you are away based on activity on the specific device.
That is inadequate. Availability should show real life availability, not PC activity.
Otherwise people might hesitate in contacting us, even though we can be working on another device or even performing another activity just a few inches away from the keyboard.
In those scenarios we need to be able to place ourselves as Available as most of the time those activities can and should be interrupted to answer an important message.
On related but not exactly the availability issue, why isn't there an audible sound when a message arrives? That is insane. If we are focused on some tasks we are not likely to even notice a little popup at the bottom right of the screen, and will miss important messages.
I am sorry to say that although Teams has some nice features, its IM portion is the most inadequate IM tool I have seen in the decades since the original IM tool was invented.
I suspect I will end up uninstalling it and return to Lync/Skype for Business on the desktop. I might keep it around on the mobile, but let people know that they should not use it for anything urgent as I am very likely to miss their messages for hours.