The package libdbd-mariadb-perl has been available in Debian September
2018, so it is already included since Debian Buster and Ubuntu Disco.

Use it as the primary Recommends for MariaDB client binaries, but keep
the MySQL variant as a fall-back in case this package gets backported to
older releases that did not yet have it.

This change was done in downstream Debian packaging in
https://salsa.debian.org/mariadb-team/mariadb-10.4/-/commit/bb4ad78bc10a1b52558c4c30600a02e30c4ce0a9