Skype as deb package discontinued and repo removed as of June 2024 and replaced with snap package only:
https://answers.microsoft.com/en-us/skype/forum/all/skype-for-linux-updates/da864865-d9e9-4819-8a5d-8de8934dd312

Alternative would be https://web.skype.com/

install skype:

wget https://go.skype.com/skypeforlinux-64.deb
sudo dpkg -i skypeforlinux-64.deb

Skype repo:

wget https://repo.skype.com/data/SKYPE-GPG-KEY
sudo apt-key add SKYPE-GPG-KEY
rm SKYPE-GPG-KEY
sudo sh -c 'echo "deb [arch=amd64] https://repo.skype.com/deb stable main" >> /etc/apt/sources.list.d/skype-stable.list'
sudo apt-get update
sudo apt-get install skype

For distorted or absent sound latency settings may be required:

env PULSE_LATENCY_MSEC=30 skype %U

gnome menu entry to be updated using: Some systems require 60

sudo sed -i 's/^Exec=.*/Exec=env PULSE_LATENCY_MSEC=30 skype %U/' /usr/share/applications/skype.desktop

If Skype doesn't start automatically with system, it needs to be added to “Startup Applications”.

Skype appears to re-create auto-start entry automatically. To prevent this:

rm ~/.config/autostart/skypeforlinux.desktop
mkdir ~/.config/autostart/skypeforlinux.desktop