kalarm 2.12.2 as installed in Debian 10 using KDE Plasma 5.14.5, Frameworks 5.54.0, and Qt 5.11.3 refuses to create new alarms or import alarms.

The "Details" button says "failed to append item."

As another user has noticed, there are tens of thousands of kalarm .ics files under .local/share/akonadi_kalarm*. Are the problems related?

More recent versions of KAlarm (version 3.0 and later, since August 2020) do not have this type of problem, and an upgrade to Debian 11 would fix it. The problem is due to Akonadi, which KAlarm stopped using in version 3.

The only old bug report which I can find which might relate to this issue is https://bugs.kde.org/show_bug.cgi?id=455377 (Akonadi/Kalarm Constant Disk Access & High CPU Usage + Creates 700,000 Files). Perhaps this will help you to get around the problem.

There are 3 possible methods to get round a problem using the Import Alarms function. (If you have KAlarm version 3 or later, the Import Alarms function should work ok).

1) If the calendar you want to import is not on your local drive, copy it to there. Once it is on your local drive, use View -> Show Calendars to display KAlarm's calendars. Then click Add... to tell KAlarm to use the calendar as an additional active alarms calendar.

2) Alternatively, you can replace your active alarms calendar with the calendar you want to import. This would wipe out any existing alarms which you have created, so wouldn't be appropriate if need to keep existing alarms. To do this, find the location of your active alarms calendar by using View -> Show Calendars to display your calendars, and hover the cursor over the Active Alarms calendar. This will display its location. Then simply copy or move the calendar to be imported to the active alarms calendar location.

3) If you need to keep existing alarms, you could manually add the contents of the calendar to be imported into the active alarms calendar by editing the calendar file using a text editor. Find the location of the active alarms calendar in the way described in 2), and open it in an editor. Then copy the contents of the calendar to import, starting from the first BEGIN:VEVENT or BEGIN:VTIMEZONE line, and excluding the last line (END:VCALENDAR). Insert the copied contents into the active alarms calendar immediately before the last line (END:VCALENDAR). The new contents should be seen by KAlarm when you save the file. If not, you need to restart Akonadi in a terminal window using the command 'akonadictl --restart'.

If you can't upgrade to KAlarm version 3, it might be worth trying to reset Akonadi for KAlarm. One method is described in https://forums.linuxmint.com/viewtopic.php?t=264682, but if you use other Akonadi applications such as KMail or KOrganizer, you need to be careful in case you lose any data from them. You could also search the internet for other ways to fix Akonadi.