No big surprise here, and I don’t think this will impact many, but Microsoft have officially announced these apps will no longer be available for download from Microsoft Store, and Microsoft will no longer support them.
- Skype for Business and Yammer apps may continue to work, but we can’t provide any guarantees. These apps will no longer receive updates or support.
- The Microsoft Teams app will no longer work, and users will receive an error message when they try to connect.
Interestingly the announcement says “Moving forward, Windows Phone users will have the best experience by using Skype for Business, Microsoft Teams, and Yammer in the mobile web browser.”. I guess “only” is also “best” 
, however SfB won’t work in a browser and I don’t believe Teams will render on a mobile browser either.
Basically the real answer in 2018 is iOS or Android.
