Workaround for install viber 7x on debian-like systems. Viber depends on libcurl3 but we have libcurl4 in repos.

viber-install-package-lock-workaround.sh

#!/usr/bin/env bash

# http://forum.linuxthebest.net/prilozheniya/viber-v-ubuntu-18-04-bionic-beaver/

apt-mark hold libcurl4
dpkg -i --ignore-depends=libcurl3 ./viber.deb
apt-mark unhold libcurl4

viber-install-rpm-debian-workaround.sh

#!/usr/bin/env bash

# https://askubuntu.com/questions/1029584/workaround-for-viber-and-libcurl3-on-ubuntu-18-04

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

viber-install-with-deb-repack.sh

#!/usr/bin/env bash

wget -O ./viber.deb http://download.cdn.viber.com/cdn/desktop/Linux/viber.deb

dpkg-deb -x viber.deb viber
dpkg-deb --control viber.deb viber/DEBIAN
#Edit viber/DEBIAN/control and repace "libcurl3" with "libcurl4"
sed -i 's/libcurl3/libcurl4/g' viber/DEBIAN/control
dpkg -b viber vibernew.deb
sudo dpkg -i vibernew.deb

viber-install-with-deb-repack.sh is a best solution