so I guess there's no way to have "clean NAND backup" afterwards but what will be the 2nd best option to get the NAND backup in this scenario?
Auto rcm ( modifies the boot partition)
If you have never used a homebrew (no log or crash error)
If you have not installed a nsp, or things like that that modify your nand, you can be clean.
Use hekaté to backup your nand, boot 0, boot 1.
Precaution
Do not share your information (switch setting)
Stealth airplane mode
Then save your nand
Otherwise to your restoration of nand
Your switch will communicate to nintendo what you don't want to do.
I've never used anything but hekate to dump the nand.
I don't have any feedback on the nand dump done with sxos ( is it reliable? I don't know)
Reinx, it is apparently not reliable, users have apparently encountered problems, error in restoration, or ban.