Newbie question. I have just installed the stable release 21.02.3 factor.bin file for my router as per website instructions. It all looks OK and looks like I have the LuCI GUI. Do I need to install the sysupgrade.bin file? I can't actually see in the instructions that I should but some YouTube videos sort of give that impression that on a new install one needs to do both. I can't actually see an option for this in menu list. Sorry to be a dummy. I'm very old.
No. The factory image is all you need when installing for the first time on many devices. The sysupgrade file is what you’ll use to move to the next version (from an existing openwrt installation)
The only time you need to “double” upgrade is if you are using an initramfs type initial install - this loads into ram and doesn’t actually use permanent storage, so you need to perform a sysupgrade in those cases to truly install OpenWrt in the flash memory.