Ubuntu 18.04 Unable to install Viber

If the deb package available in the viber website is not installing, or creating some error, then you can try downloading the rpm package and converting it to deb:

wget https://download.cdn.viber.com/desktop/Linux/viber.rpm

Install alien, convert the rpm package and install the newly created deb package:

sudo apt-get install alien
sudo alien --to-deb --scripts viber.rpm
sudo dpkg -i viber_7.0.0.1035-3_amd64.deb

The conversion will take about 5 minutes. Be patient!

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