Turn off calendar notifications - Ubuntu 20.04

If you added online accounts, go to settings > Applications > calendar, then turn off notifications

Or you can go to settings > online accounts > google account and turn of this one:

Currently it's the way how evolution notification daemon is working. If u want to disable just reminders, but keep notifications you can do it by so:

edit file /etc/xdg/autostart/org.gnome.Evolution-alarm-notify.desktop and change the line OnlyShowIn=GNOME;Unity;XFCE;Dawati;MATE; to -> NotShowIn=GNOME;

Now keep in mind, that you can replace GNOME by any distro you're using.

Edit: Formatting

You can suppress the ugly pop-up window – but keep the less obtrusive Gnome Shell notification – by setting /org/gnome/evolution-data-server/calendar/notify-with-tray in dconf.

I discovered this from a comment in a related evolution-data-server bug report (GNOME/evolution-data-server#60).

Steps

Install dconf Editor if it's not already installed:

sudo apt install dconf-editor

Launch dconf Editor:

Navigate to /org/gnome/evolution-data-server/calendar and set notify-with-tray to "on":