Hello! Can you please test again with the latest version in Debian unstable and verify this is fixed now?
MariaDB 10.3 in Debian has a rather extensive testing suite at https://salsa.debian.org/mariadb-team/mariadb-10.3/pipelines/41873 If you would like to contribute and write a new section to our gitlab-ci.yml file that automatically does Akonadi things and runs mysql_install_db if would ensure regressions like these don't creep in unnoticed in the future.
