https://download.cdn.viber.com/cdn/desktop/Linux/viber.deb

  1. Save the viber.deb file in a folder
  2. Open the folder in a terminal
  3. execute the following commands
  4. dpkg-deb -x viber.deb viber
  5. dpkg-deb --control viber.deb viber/DEBIAN
  6. Edit viber/DEBIAN/control and replace “libcurl3” with “libcurl4” (also delete the last blank line from the file or you will get an error afterwards)
  7. dpkg -b viber viberlibcurl4.deb
  8. sudo dpkg -i viberlibcurl4.deb or install the .deb file with gdebi

 

Source: https://askubuntu.com/questions/1030479/ubuntu-18-04-unable-to-install-viber