I'm not sure it's a bug. You use --skip-opt which, besides other things, means that mariadb-dump should not include table/field/index options into the table definition. MySQL has removed those sql_mode values, meaning, when you dump from MySQL, mariadb-dump is unable to do what you requested, the dump from MySQL will always include table/field/index options.
MySQL "fix" was to ignore user's explicit request, see their commit, the test uses --skip-create-options and the dump contains create options regardless. This looks more like a bug "mysqldump ignores --skip-create-options", than the fix,
I think an error is quite appropriate here, you asked mariadb-dump to do something that it cannot do.
I'm not sure it's a bug. You use --skip-opt which, besides other things, means that mariadb-dump should not include table/field/index options into the table definition. MySQL has removed those sql_mode values, meaning, when you dump from MySQL, mariadb-dump is unable to do what you requested, the dump from MySQL will always include table/field/index options.
MySQL "fix" was to ignore user's explicit request, see their commit, the test uses --skip-create-options and the dump contains create options regardless. This looks more like a bug "mysqldump ignores --skip-create-options", than the fix,
I think an error is quite appropriate here, you asked mariadb-dump to do something that it cannot do.