I'm on: KDE neon User Edition 5.15 Release 18.04, bionic.

I installed Kalarm from the Discover programs option that goes to the main repository for the disto.

When starting Kalarm, the New Alarm and various other options were grayed out.

On rebooting, Kalarm auto started and gave a series of errors.

"Akonadi Alarm Resources Closed Unexpectedly"
"Failed to create default calendar archived alarms"
"Failed to create default calendar active alarms"
"Failed to create default calendar alarm template"

This bug has recently been fixed - see https://bugs.kde.org/show_bug.cgi?id=407544. The fix will be in KDE Applications 19.04.2, due to be released on 6th June.

djarvie wrote:This bug has recently been fixed - see https://bugs.kde.org/show_bug.cgi?id=407544. The fix will be in KDE Applications 19.04.2, due to be released on 6th June.

Great, where do I get the new version when it is out?

As far as I know, Neon should provide updated packages each time a new KDE applications release comes out. See https://neon.kde.org/faq#command-to-update for details about how to update the Neon system.