After a (no) decision was taken at T193224, tracking the progress in an epic task of our progress of upgrading all databases, and services around them (monitoring, backups, etc.) to Debian Buster and MariaDB 10.4.
MariaDB 10.1 EOL 17th Oct 2020: https://mariadb.com/wp-content/uploads/2019/07/mariadb-engineering-policies-v2-01_policy_1036.pdf