Install Skype from repository

wget https://raw.githubusercontent.com/panticz/installit/master/install.skype.sh -O - | bash -

#!/bin/bash

# add skype repository
echo "deb [arch=amd64] https://repo.skype.com/deb stable main" | sudo tee /etc/apt/sources.list.d/skype-stable.list

# add repository key
wget https://repo.skype.com/data/SKYPE-GPG-KEY -qO- | sudo apt-key add -

# update
sudo apt-get update -qq

# install requirements
sudo apt install -y apt-transport-https

# install skype
sudo apt install -y skypeforlinux

Fix upside down webcam
wget https://raw.githubusercontent.com/panticz/scripts/master/fix_skype_upsidedown_webcam.sh -O - | bash -

#!/bin/bash

# install video4linux libraries 
sudo apt-get install libv4l-0:i386

# fix lib path
if [ ! -f /usr/lib/libv4l/v4l1compat.so ]; then
  sudo mkdir /usr/lib/libv4l
    if [ "$(uname -m)" == "x86_64" ]; then
      # 64 bit
      sudo ln -s /usr/lib/x86_64-linux-gnu/libv4l/v4l1compat.so /usr/lib/libv4l/v4l1compat.so
    else
      # 32 bit
      sudo ln -s /usr/lib/i386-linux-gnu/libv4l/v4l1compat.so /usr/lib/libv4l/v4l1compat.so
  fi
fi

# modify Skype launcher
sudo sed -i 's|env PULSE_LATENCY_MSEC=60 skype %U|env PULSE_LATENCY_MSEC=60 LD_PRELOAD=/usr/lib/i386-linux-gnu/libv4l/v4l1compat.so skype %U|g' /usr/share/applications/skype.desktop

Install with snap
sudo snap install skype --classic

Disable "contacts comes online" notification
# Notify
sed -i 's|1|0|g' /home/${USER}/.Skype/*/config.xml
sed -i 's|1|0|g' /home/${USER}/.Skype/*/config.xml

# Sound
sed -i 's|1|0|g' /home/${USER}/.Skype/*/config.xml
sed -i 's|1|0|g' /home/${USER}/.Skype/*/config.xml

Links
https://www.linuxbabe.com/ubuntu/install-skype-ubuntu-18-04-lts-desktop
http://wiki.ubuntuusers.de/Canonical_Partner - Ubuntu partner repository
http://www.semanticpool.de/hidden-skype-emoticons/ - hidden skype emoticons
https://help.ubuntu.com/community/SkypeTroubleshooting
https://wiki.ubuntu.com/SkypeWebCams