It seems that it is enabled on a fresh Discourse docker image (running Debian 10). It is launched through runit -> cron -> /etc/cron.daily/apt-compat -> /usr/lib/apt/apt.systemd.daily
It was also running on a one-year-old Ubuntu 16-based docker image (based on discourse/base:2.0.20190321-0122), I am pretty sure without any customization.