I’m excited to announce that setting a custom status message is in internal testing, and should be coming soon! Thanks! ~ AlexMarco Erdmann commented
Just found this feature in the newest Teams update. While it is in principle nice to have this back (we were using Skype for Business before), this has to get more prominent. It currently only shows up in the Avatar popup which is way to invisible. My colleagues use it to notify others e.g. about home office or other relevant information so it would be nice to see this also in the chat list without hovering the mouse over the avatar picture.