Severity: wishlist Version 1:10.11.5-3 You are correct in that there are still calls to '--defaults-file=/etc/mysql/debian.cnf' in the package scripts and that they have been deprecated.
They are obsolete on new installs. However on old installs that upgraded from MariaDB 10.x they are still needed. We likely have to wait for several years before removing those, and additionally there needs to be scripts that delete/rename the all the legacy /etc/mysql/debian.cnf files before that.