/usr/mips-linux-gnu/lib32/libthread_db.so.1 is in libc6-mipsn32-mips-cross 2.23-0ubuntu3cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/mips-linux-gnu/lib32/libthread_db-1.0.so
/usr/mips-linux-gnu/lib32/libthread_db-1.0.so