Hi Dave, Thanks for the detective work! :-) Interesting! One possible Debian-side solution could be changing the virtual-mysql-client-core and virtual-mysql-server-core to mariadb-client-core and mariadb-server-core, default-mysql-server to mariadb-server and removing the default-mysql-server-core dependency. That would cause dependency issues on systems that already have mysql-server-8 installed, but since CQRLOG does not seem to work with mysql anymore (only with mariadb), it should not be a big problem, at least in my opinion.
The other possible solution would be - as you suggested - to patch this in Ubuntu. However, I am not sure whether the CQRLOG package has any Ubuntu maintainers and also it would probably break auto-sync of the package from Debian. Anyway, I will also comment on this in the original Ubuntu Launchpad ticket and we'll see if there is any progress. :-) Thanks! Regards, Daniel (OK2VLK)