What causes apparently random “digital watch” beeping alarms on F32?

Context

I have recently updated from Fedora 31 to Fedora 32 (on a Thinkpad X1 Carbon — but I’m not sure it’s relevant).

Problem

Since the update, I’m experiencing beeping alarm sound at apparently random times; which is quite annoying.

What I’ve noticed so far:

• The alarms sounds like “a digital watch alarm”, as described in this subreddit. However, unlike what the feedback comment says, it didn’t stopped after a dnf upgrade for me. Moreover, I’ve only used post-released Fedora 32, and not beta (as in the subreddit).
• The alarm sound is different from the terminal bell / alert sound.
• The alarm goes off about a couple times a day. It lasts around 10 seconds. Time seems consistent from day to day, and to occur at “round times”: e.g., 08:50, 12:15, etc.

• Alarms do not seem to be related to any calendar event. As far as I remember, they were still here when I uninstalled GNOME-Calendar.

• Alarms are not related to GNOME-Clocks alarms.

• There are no cron jobs running (neither for my user, nor for root)

Questions

What causes these alarms? How to disable them?