It has finally happened. Microsoft today killed the classic Skype application for Linux. Skype 4.3 was built against the native Qt toolkit and was very lightweight on system resources. It remained very popular among Linux users even when a new Electron-based version of Skype was released.
As you may remember, a few days ago Microsoft announced that Skype versions which utilize the P2P protocol will be discontinued on March 1st, 2017. This will affect certain versions of Skype for Windows and macOS. It was assumed that the classic Linux version of the app will stop working as well, because it is using the P2P protocol too. But for now, it's going to continue to work.
Starting March 1, 2017, Microsoft is going to discontinue certain older Skype versions. For Windows, you need at least Skype 7.16, for macOS, you'll need Skype 7.18 and for Linux, you will probably need the newest alpha version of Skype.