Just use apt-cache policy to find the repo of a package: apt-cache policy lxd lxd: Installed: 3.0.3-0ubuntu1~18.04.2 Candidate: 3.0.3-0ubuntu1~18.04.2 Version table: *** 3.0.3-0ubuntu1~18.04.2 500 500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages &nb........

These types of errors are normally caused by misconfiguration of your /etc/apt/sources.list. In this example on Debian 10, if you didn't complete the install correctly, you will have no repos enabled and only rely on CDROM. "Package wget is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source. E: Package 'wget' ha........

The Linux Mint team has disabled it by setting an apt preference, you can edit or just remove the file: sudo apt install snapd Reading package lists... Done Building dependency tree Reading state information... Done Package snapd is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source........

Idon't know why but some installations don't have this in the database by default. To fix it to an: sudo apt-get update;sudo apt-get install openssh-server and then it will work........