I don’t use the standard/built-in calendar app (I use digical) and the toggle to turn off app notifications for the calendar app is greyed out. So notifications for calendar can’t be disabled.
This results in every event notification happening twice. It’s crazy-making.
I see a handful of topics here that don’t seem to really be resolved.
I could not register on gitlab to to file a bug report or comment on this closed issue from 5 years ago that seems to recur(?):
the gist: disable each calendars sync selectively through the accountmanager (davx fork) settings. Should also work at one level above where you disable the sync type.
stepped right into that sorry. It would make sense if digical is managing the calendar in-App, not the system backend.
The user in the linked answer writes “I didn’t start the system calendar anymore” (what I assume mean force-stopped via Settings → Apps) - which I thought to work only until reboot, but apparently I noticed the service still stopped after reboot, not giving alerts that digical acted upon. Worth to look into how long that force-stop sticks?
The linked solution from yours truly does not work with all calendars: While Fossify Calendar continues to synchronize and show all scheduled events, this was not the case when I tested aCalendar, which another user has chosen as default calendar. aCalendar did no longer show the events when they were not visible in the system calendar app - so you still get double notifications if you want to use e.g. aCalendar.
A not ideal workaround: Deactivate the system calendar notifications sound
Open app info of the calendar app (Settings > Apps > Show all apps > Select System Calendar app)
Open Notifications entry
There should be a message channel shown for each calendar.
For each calendar
Tap on its entry
Set notification sound to “none” (or something similar)
Adapt additional settings if desired (and available)
I am not sure whether this is a suitable workaround - your mileage will vary.
I hope that /e/OS will offer a better option in the near future.
EDIT: As this UX problem frequently comes up, maybe @Manoj can “nudge” the developers to take a look? @tcecyk’s comment in GitLab seems to describe an easy fix.