MySQL Plugin failed to install due to "undefined symbol"

For several years now I have used the MariaDB Audit Plugin on my MySQL databases.

I am now looking to start Upgrading my databases to MySQL 8, and so have just tried installing it onto MySQL 8.0.19, but am getting the following error:

Error Code: 1126. Can't open shared library '/usr/lib/mysql/plugin/server_audit.so' (errno: 2 /usr/lib/mysql/plugin/server_audit.so: undefined symbol: fn_format)

I tried downloading the latest version (audit 1.4.7 from the MariaDB 10.4.7 binaries) but it made no difference. Downloading older versions of the plugin also made no difference.

Is this likely to be a MySQL problem or a Mariadb problem? And is there a way to get round this. Most of my databases are installed on Debian 9 or 10 servers.