/usr/share/man/man3/log_flush.3debug.gz is in libdebug0-dev 0.4.4-1.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man3/log_open.3debug.gz
/usr/share/man/man3/log_open.3debug.gz