/usr/riscv64-linux-gnu/lib/libnss_nis.so is in libc6-dev-riscv64-cross 2.27-3ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/riscv64-linux-gnu/lib/libnss_nis.so.2
/usr/riscv64-linux-gnu/lib/libnss_nis.so.2