/usr/x86_64-linux-gnu/lib32/libthread_db.so.1 is in libc6-i386-amd64-cross 2.27-3ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/x86_64-linux-gnu/lib32/libthread_db-1.0.so
/usr/x86_64-linux-gnu/lib32/libthread_db-1.0.so