Comment 7 for bug 1797643

I can reproduce this on Neon 18.04 user edition on a fresh install, and using Kubuntu CI builds of apps/akonadi stable 18.08 branch.

(1) I am not sure it was intentional for Neon to switch to mariadb. This may be a result of the packaging for the mysql backend having:

Depends: libqt5sql5-mysql,
         mysql-client-core-5.6 | virtual-mysql-client-core,
         mysql-server-core-5.6 | virtual-mysql-server-core,

whereas mysql 5.6 package do not exist in Bionic (5.7 is there) so mariadb gets pulled in instead.

(2) This looks very similar to https://bugs.kde.org/show_bug.cgi?id=392948 which was supposedly fixed.

I would note that the same result and workaround

mkdir -p ~/.local/share/akonadi/db_data/

before starting akonadi for the 1st time, works with both mariadb on Neon and mysql on Kubuntu.