[Kde-pim] KDE-PIM issue after upgrading to MariaDB

Hello,

Using kUBUNTU 18.04. I wanted to upgrade mySQL to MariaDB. The upgrade 
did run well so I removed mySQL and installed MariaDB, which runs OK 
now. Furthermore I moved the DataDir from /var/lib/mysql to 
/mnt/driveX/.../mySQL. Also this is fine with several Databases.

Now I wanted to start kAlarm again, which has been installed earlier. 
First it was claiming about "Akonadi not running" and I fixed it as 
mentioned here 
<https://mail.kde.org/pipermail/kdepim-users/2017-August/000858.html>:
akonadictl stop
rm -r ~/.local/share/akonadi
akonadictl start

Now I have:
$ akonadictl status
Akonadi Control: running
Akonadi Server: running
Akonadi Server Search Support: available (Remote Search)
Available Agent Types: akonadi_indexing_agent

$ kalarm
org.kde.pim.kidentitymanagement: IdentityManager: There was no default 
identity. Marking first one as default.
The kAlarm GUI window is claiming about "No Akonadi Agents available, 
check KDE-PIM-Installation".

How can I solve this KDE-PIM issue?

Thanks, Michael