unknown variable ‘file-key-management-filename’

New installation of Debian 10, with MariaDB 10.3.29. Trying to set up encryption-at-rest, but MariaDB won’t start due to an error…

[ERROR] /usr/sbin/mysqld: unknown variable 'file-key-management-filename=/etc/openssl/keys/keyfile.key' 

My server.cnf has…

[mariadb-10.3] plugin-load-add = file_key_management file_key_management_filename = /etc/openssl/keys/keyfile.key file_key_management_encryption_algorithm = AES_CTR 

The above config I have working in a Centos7 system, so I’m baffled as to why it isn’t working on Debian10. This message is what I encountered when trying to install encryption in a MariaDB pre-10.1 version that didn’t have encryption as an option, but I know encryption is an option after Mariadb 10.1, so it should be available in this package (unexciting installation via apt), right? I have tried moving the cnf code around, to the [mysqld] and [mariadb] sections to no avail. There are no previous versions of MariaDB hanging around – this is a clean install.

Has anyone encountered this issue and solved it already?