My results:
O3DS 10.1.0-27E to 9.2.0-20E downgrade successful
- Set up sysUpdater and updates folder with .cia files on SD card
- Launched sysUpdater through HomeMenuHax
- Installed 9.2.0 .cia files
- Reboot to black screen
- Removed SD card
- Booted up
- Inserted SD card
- Accessed homebrew launcher via Cubic Ninja cart
- Reset HomeMenuHax
- Copied PastaCFW files to SD
- Successfully booted PastaCFW via HomeMenuHax
After reading the posts on bricked N3DS units, I decided against downgrading until it's more stable. Out of curiosity though, I tried launching sysUpdater just to see if it would even open properly (without the 9.2.0 N3DS .cia update files on the SD card to prevent accidental installation).
N3DS XL test results
- Initially on 10.1.0-27E
- Opened HomeMenuHax Manager via HomeMenuHax
- Deleted HomeMenuHax through manager
- Reboot, updated to 10.3.0-28E via system settings
- Reinstalled NinjHax onto Cubic Ninja cart*
- Reinstalled IronHax through Ninjhax on Cubic Ninja cart*
- Reinstalled HomeMenuHax through IronHax*
- Copied sysUpdater to /3ds/ without the 9.2.0 .cia files
- Attempted to open sysUpdater through HomeMenuHax/IronHax
- Stuck at step 5 or 7
- Reboot, launched LibRetro GPSP through HomeMenuHax
- Allowed it to run idle for about 5 minutes
- Exit to homebrew launcher, launched sysUpdater
- Successful launch, able to access menu for downgrade
So far I'm able to get up to the point where the 3DS is ready to downgrade, but I haven't started any downgrade process in case sysUpdater crashed halfway through and bricked my console. Theoretically it should work but it's not a risk I want to take at the moment.
* In case anyone's wondering about the large number of homebrew entrypoints installed, HomeMenuHax is my main entrypoint with IronHax as a fallback. Cubic Ninja is the last resort if both fail, and is used between multiple consoles as a permanent entrypoint in case the other two are somehow damaged through accidental updating and whatnot.