my apologize... nand tools are available in OpenWrt !
root@ultra:~# opkg install nand-utils
Installing nand-utils (2.1.2-1) to root...
Downloading https://downloads.openwrt.org/releases/21.02.0-rc3/targets/mvebu/cortexa53/packages/nand-utils_2.1.2-1_aarch64_cortex-a53.ipk
Configuring nand-utils.
nanddump nandtest nandwrite
Usage: nanddump [OPTIONS] MTD-device
Dumps the contents of a nand mtd partition.
-h --help Display this help and exit
--version Output version information and exit
--bb=METHOD Choose bad block handling method (see below).
-a --forcebinary Force printing of binary data to tty
-c --canonicalprint Print canonical Hex+ASCII dump
-f file --file=file Dump to file
-l length --length=length Length
-n --noecc Read without error correction
--omitoob Omit OOB data (default)
-o --oob Dump OOB data
-p --prettyprint Print nice (hexdump)
-q --quiet Don't display progress and status messages
-s addr --startaddress=addr Start address
--skip-bad-blocks-to-start
Skip bad blocks when seeking to the start address
--bb=METHOD, where METHOD can be `padbad', `dumpbad', or `skipbad':
padbad: dump flash data, substituting 0xFF for any bad blocks
dumpbad: dump flash data, including any bad blocks
skipbad: dump good data, completely skipping any bad blocks (default)
root@ultra:~# nandtest
usage: nandtest [OPTIONS] <device>
-h, --help Display this help output
-V, --version Display version information and exit
-m, --markbad Mark blocks bad if they appear so
-s, --seed Supply random seed
-p, --passes Number of passes
-r <n>, --reads=<n> Read & check <n> times per pass
-o, --offset Start offset on flash
-l, --length Length of flash to test
-k, --keep Restore existing contents after test
root@ultra:~# nandwrite
Usage: nandwrite [OPTION] MTD_DEVICE [INPUTFILE|-]
Writes to the specified MTD device.
-a, --autoplace Use auto OOB layout
-k, --skip-all-ffs Skip pages that contain only 0xff bytes
-m, --markbad Mark blocks bad if write fails
-n, --noecc Write without ecc
-N, --noskipbad Write without bad block skipping
-o, --oob Input contains oob data
-O, --onlyoob Input contains oob data and only write the oob part
-s addr, --start=addr Set output start address (default is 0)
--skip-bad-blocks-to-start Skip bad blocks when seeking to the start address
-p, --pad Pad writes to page size
-b, --blockalign=1|2|4 Set multiple of eraseblocks to align to
--input-skip=length Skip |length| bytes of the input file
--input-size=length Only read |length| bytes of the input file
-q, --quiet Don't display progress messages
-h, --help Display this help and exit
-V, --version Output version information and exit
so, as said in linux MTD :
It is better to use nanddump and nandwrite...
for backup and restore nand (MTD) partitions !