4.15.0-44.47) is not available, but a newer one is (4.15.0-46.49). We redirected you there.
/usr/sbin/maas-region-admin is in maas-region-api 2.0.0~beta3+bzr4941-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/sbin/maas-region