mark@mark-Inspiron-3847:~ $ sudo apt-cache policy gdm3
gdm3:
  Installed: (none)
  Candidate: 3.28.2-0ubuntu1.4
  Version table:
     3.28.2-0ubuntu1.4 500
        500 http://gb.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
     3.28.0-0ubuntu1 500
        500 http://gb.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
mark@mark-Inspiron-3847:~ $