As others are saying, the new Electron-based app is so bad on so many levels. Recently it has been failing to deliver incoming messages. They don't even appear, it just causes confusion to anyone trying to have a text conversation. Plus the lack of features that versions for other platforms have.
At this point it's just better to use web.skype.com on a browser tab. I find that more reliable than the Electron client.
And I'm just talking about the Linux version here. It's like if Skype had different bugs on each platform. Windows version also has its own glitches too.
* The classic, full version of Skype for Windows sometimes flips the order of a few messages, so that if you send two messages, the first one appears below the second one.
* The new UWP app seems to disconnect every time the window gets minimized. When the window is restored, for a few seconds I see all my contacts offline while it's trying to reconnect.