A future version of MariaDB might have the charsets in its own directory, but we can't start changing paths of stuff in existing stable releases, such as MariaDB 10.3 in Ubuntu 20.04 or Debian Buster. If MySQL introduces a backwards incompatible change, the new uploads should test for them and work around issues discovered.
In MariaDB we are building python-mysql against libmariadb on every commit in the CI to ensure nothing is broken: https://salsa.debian.org/mariadb-team/mariadb-10.3/pipelines If you think MythTV has something unique about this, we could add MythTV builds to the CI to ensure new uploads of MariaDB does not break MythTV builds in Debian?