Your package has a preinst maintainer script, calling adduser. At the same
time, your package Depends: adduser, but does not Pre-Depends: adduser.
Installing your package fails when adduser is not yet configured.

Reproducer:

$ mmdebstrap --variant=essential --include=ganglia-monitor unstable /dev/null
...
Selecting previously unselected package ganglia-monitor.
Preparing to unpack .../20-ganglia-monitor_3.7.2-7_arm64.deb ...
dpkg-statoverride: error: user 'ganglia' does not exist
dpkg: error processing archive /tmp/apt-dpkg-install-PCHLEB/20-ganglia-monitor_3.7.2-7_arm64.deb (--unpack):
 new ganglia-monitor package pre-installation script subprocess returned error exit status 2
Errors were encountered while processing:
 /tmp/apt-dpkg-install-PCHLEB/20-ganglia-monitor_3.7.2-7_arm64.deb
E: Sub-process env returned an error code (1)



You may consider replacing adduser with a sysusers fragment, see
https://manpages.debian.org/unstable/debhelper/dh_installsysusers.1.en.html

Otherwise, please Pre-Depend on adduser.

Best,
Chris