yes reading the documentation.SO DO NOT DOWNGRADE FROM FW 20 BECAUSE YOUR USER PARTITION WILL BE BROKEN.
use Daybreak Homebrew to install any previous firmware
My stupid ass accidentally downgraded firmware 20.5.0 to 19.0.1 on sysMMC using Daybreak, because I thought my old Switch still was on firmware 18. It wasn't. This resulted in error 2002-3005 (0x177a02) 0100000000000025.Dont do that.
User partition will be corrupted and you'll need to format from recovery!
However, when booting into recovery mode (vol down + vol up during boot), I was able to update firmware from there to 20.5.0 again and everything seems fine. But... is it? How will I know my user partition is broken?













