Debian is a Linux-based operating system available for a wide range of devices including laptops, desktops and servers. Debian comes with over 60000 packages (precompiled software that is bundled up in a nice format for easy installation on your machine).
The Debian developers provide updates for all packages over their lifetime whenever possible. Even if the Linphone package has been distributed on Debian since 2013, it was stuck to version 3.12 (old GTK-based version).
Thanks to the great help of Debian packagers, and with some help from our Linphone-desktop lead developper, the latest Qt-based Linphone version (4.2.5) is now properly packaged and distributed on Stable (the official Debian release).
We recommend all fellow Debian users to move to Linphone 4.X, as we do not support 3.X versions anymore. That way, you will also benefit from all the new features, improvements and bug fixes we have made in Linphone over the past couple of years.