Debian is an operating system based on Linux.
The distribution contains a huge collection of open source software.
After Debian has been installed, I recommend having a look at
post_install_deb.sh, which is found at the bottom of this page.
The Advanced Package Tool (APT) is used to search, install and remove
software packages in Debian. APT has advanced features like the following.
List removed packages with residual config files:
apt list ?config-files
Find packages that are no longer available in any configured APT repository:
apt list ?obsolete