Disable automatic S.M.A.R.T. tests

I have a small (single-board) Zimaboard server that is running Debian 12 (bookworm) 24/7 in my bedroom. This server has a single HDD hooked-up, which remains unmounted and in sleep mode except for a daily back-up cycle (after which it is unmounted and goes back to sleep). Unfortunately, every Monday at 00:45 AM the server decides to wake up the HDD (and myself...) to execute what sounds like a short S.M.A.R.T test. I then have to grab my phone and issue a sleep command to stop the HDD from making its typical HDD noises afterwards (humming, occasional clicks, ...). As you can imagine, this is incredibly annoying, so I want to fix it. I first looked for crontab schedules (executed as user or root), but I didn't see anything relevant. journalctl --since ... --until ... didn't report anything useful either. The only uncommented line in /etc/smartd.conf says: DEVICESCAN -d removable -n standby -m root -M exec /usr/share/smartmontools/smartd-runner. I don't see anything there that could point to a weekly maintenance schedule. Is there any way to find out what triggered the S.M.A.R.T. test (or similar)? Where do I look for log entries? And how do I prevent it from executing in the middle of the night?