/usr/arm-linux-gnueabihf/lib/libthread_db.so.1 is in libc6-armhf-cross 2.27-3ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/arm-linux-gnueabihf/lib/libthread_db-1.0.so
/usr/arm-linux-gnueabihf/lib/libthread_db-1.0.so