Backing up original firmware on tp-link er605v2

Installing and Using OpenWrt
1

What is the proper method to backup factory firmware on er605v2? I want to back up everything before flashing openwrt so I could restore factory firmware in future.

Hardware Version:ER605 v2.0

Firmware Version:2.1.2 Build 20230210 Rel.62992

I want to flash https://downloads.openwrt.org/releases/23.05.0/targets/ramips/mt7621/openwrt-23.05.0-ramips-mt7621-tplink_er605-v2-initramfs-kernel.bin

2

Take a look here Looking for info and possibility of (future) support of TP-Link Omada er605 Router

You'll find how to flash and backup.