lsblk is not a default package on any platform that I'm aware, so you need to install it on any fresh install:
$ opkg update
$ opkg -A info lsblk
Package: lsblk
Version: 2.39-2
Depends: libc, libblkid1, libmount1, libsmartcols1
Status: unknown ok not-installed
Section: utils
Architecture: mips_24kc
Size: 63444
Filename: lsblk_2.39-2_mips_24kc.ipk
Description: lsblk lists information about all or the specified block devices
$ opkg install lsblk
...
https://openwrt.org/packages/pkgdata/lsblk
Oh, just had a thought! This is very unlikely, but maybe the package database is corrupted. Do these steps and see if it works:
Remove the package lists (the rm).
Restore the package lists (the update).
See if some package you don't have is available (the info).
Try to install it, I picked lscpu, but anything you like is fine.
$ rm /tmp/opkg-lists/*
$ opkg update
$ opkg -A info lscpu
$ opkg install lscpu
來源：https://forum.openwrt.org/t/solved-openwrt-cannot-find-lsblk-sometimes/187001/2
同理可以安裝
opkg -A info smartmontools
opkg install smartmontools
opkg -A info parted
opkg -A info