Being released at the end of last week was Viber 4.2 for Linux that replaces the badly outdated version. The Windows version for a while has been up to version 4.2 along with the iOS and Android ports while the Linux client remained very dated. Finally, the Linux client was updated with many bug-fixes and a matching feature set to Viber 4.2 for Windows with this VoIP/chat program.
Viber for Linux was originally released natively back in 2013. Viber for Linux can be downloaded at Viber.com and the binary blob is officially tested by the company just against Ubuntu Linux.