Konact / KMail does not want to start anymore, because Akonadi fails. I am not able to start akonadi

~$ akonadictl --verbose start

Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)

org.kde.pim.akonadiserver: Starting up the Akonadi Server...

org.kde.pim.akonadiserver: Found mysql_install_db:  "/usr/bin/mysql_install_db"

org.kde.pim.akonadiserver: Found mysqlcheck:  "/usr/bin/mysqlcheck"

org.kde.pim.akonadiserver: Using mysqld: "/usr/sbin/mysqld-akonadi"

org.kde.pim.akonadicontrol: Service ":1.89" owner changed from "" to ":1.89"

org.kde.pim.akonadicontrol: Service ":1.90" owner changed from "" to ":1.90"

org.kde.pim.akonadiserver: mysqld reports version 10.3.34 (MariaDB)

org.kde.pim.akonadiserver: Executing: "/usr/sbin/mysqld-akonadi" "--defaults-file=/home/raeg/.local/share/akonadi/mysql.conf --datadir=/home/raeg/.local/share/akonadi/db_data/ --socket=/run/user/1000/akonadi/mysql.socket --pid-file=/run/user/1000/akonadi/mysql.pid"

org.kde.pim.akonadiserver: database server stopped unexpectedly

org.kde.pim.akonadiserver: Database process exited unexpectedly during initial connection!

org.kde.pim.akonadiserver: executable: "/usr/sbin/mysqld-akonadi"

org.kde.pim.akonadiserver: arguments: ("--defaults-file=/home/raeg/.local/share/akonadi/mysql.conf", "--datadir=/home/raeg/.local/share/akonadi/db_data/", "--socket=/run/user/1000/akonadi/mysql.socket", "--pid-file=/run/user/1000/akonadi/mysql.pid")

org.kde.pim.akonadiserver: stdout: ""

org.kde.pim.akonadiserver: stderr: "2022-05-10 15:12:03 0 [Note] /usr/sbin/mysqld-akonadi (mysqld 10.3.34-MariaDB-0ubuntu0.20.04.1) starting as process 7312 ...

"

org.kde.pim.akonadiserver: exit code: 1

org.kde.pim.akonadiserver: process error: "Unknown error"

org.kde.pim.akonadiserver: terminating connection threads

org.kde.pim.akonadiserver: terminating service threads

org.kde.pim.akonadiserver: stopping db process

org.kde.pim.akonadiserver: Failed to remove runtime connection config file

org.kde.pim.akonadiserver: Shutting down AkonadiServer...

org.kde.pim.akonadicontrol: Service ":1.90" owner changed from ":1.90" to ""

org.kde.pim.akonadicontrol: Application '/usr/bin/akonadiserver' exited normally...

Trying to update MariaDB

I read, that I should update MariaDB, but I do not know how.

~$ sudo systemctl restart mariadb

Failed to restart mariadb.service: Unit mariadb.service not found.

~$ sudo mysql_upgrade

Reading datadir from the MariaDB server failed. Got the following error when executing the 'mysql' command line client

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)

FATAL ERROR: Upgrade failed

~$ sudo mariadb-upgrade

sudo: mariadb-upgrade: Command not found

~$ mariadb --version

mariadb  Ver 15.1 Distrib 10.3.34-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2

Then I ran

curl -LsS https://downloads.mariadb.com/MariaDB/mariadb_repo_setup | sudo bash -s -- --mariadb-server-version=10.8

sudo apt update && sudo apt upgrade -y

~$ mariadb --version

mariadb  Ver 15.1 Distrib 10.3.34-MariaDB, for debian-linux-gnu (x86_64) using readline 5.2

But as one can see, that did not change much.

I read, https://bbs.archlinux.org/viewtopic.php?id=184192, that the update to MariaDB version 10 might be the problem. It suggests to downgrade and then do some stuff and then upgrade again. However, that article is from 2014, so I am not sure that it still applies.

AppArmor

According to Upgrade to Ubuntu 20.04.2 LTS breaks Akonadi and thus KMail it might be an issue with apparmor, so I ran

sudo systemctl disable apparmor

and rebooted, but that did not help.

What can I do?