/etc/update-motd.d/50-freedombox is in freedombox-setup 0.12.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17  | #!/bin/sh
cat <<"EOF"
                         .--._    _.--.
                        (     \  /     )
                         \     /\     /
                          \_   \/   _/
                           /        \
                          (    /\    )
                           `--'  `--'
                           FreedomBox
FreedomBox is a pure blend of Debian GNU/Linux.  FreedomBox manual is
available in /usr/share/doc/plinth.
EOF
 |