If you are on Linux, you likely already have Python 3. Check by opening a terminal and entering python3 -V. If this returns a version number, it will work for this guide.
Instructions
Section I - Prep Work
Power on your console with the SD card inserted
Open Mii Maker
Wait for your console to reach the "Welcome to Mii Maker" screen, then exit Mii Maker
Power off your console
Insert your console's SD card into your computer
Copy everything inside the SDMC folder from the Release .zip to the root of the SD card, overwriting any existing files
Execute the mset9.py script on the root of the SD card
Windows: Double-click mset9.bat
If that doesn't work, shift+right-click empty space in the file explorer while in the root of your consoles SD card, select Open in Powershell/Terminal and enter py -3 mset9.py there
Linux: open a Terminal window, cd to the root of your SD card, then type python3 mset9.py and press Enter
You should see a window that says "MSET9 ... SETUP by zoogie"
Type 1, then press Enter to setup MSET9
Once the window says "Done", insert the SD card into your console
Power on your console
Section II - MSET9
These instructions must be followed exactly, so double-check everything you are doing to avoid errors.
Hover over the System Settings icon using the D-Pad (do not select it yet)
Power off, then power on your console
Press (A) to launch System Settings
Navigate to Data Management -> Nintendo 3DS -> Extra Data
Do not press any buttons or touch the screen - ensure that you see the Mii Maker icon
With the console STILL ON, and without pressing any buttons or touching the screen, remove the SD card from your console
Insert the SD card into your computer
Execute the mset9.py script on the SD card root
Windows: Double-click mset9.bat
If that doesn't work, shift+right-click empty space in the file explorer while in the root of your consoles SD card, select Open in Powershell/Terminal and enter py -3 mset9.py there
Linux: open a Terminal window, cd to the root of your SD card, then type python3 mset9.py and press Enter
You should see a window that says "MSET9 ... SETUP by zoogie"
Type 2, then press Enter to trigger MSET9
Insert the SD card into your console without pressing any buttons or touching the screen
If the exploit was successful, you will have booted into SafeB9SInstaller
If you get a black screen, the exploit may not have worked properly
If you get a red screen, you didn't copy all contents of the SDMC folder in the Release .zip to the root of your SD card
Section III - Installing boot9strap
When prompted, input the key combo given on the top screen to install boot9strap
Once it is complete, press (A) to reboot your console
Your console should have rebooted into the Luma3DS configuration menu
Luma3DS configuration menu are settings for the Luma3DS custom firmware. Many of these settings may be useful for customization or debugging
For the purpose of this guide, these settings will be left on default settings
If your console shuts down when you try to power it on, ensure that you have copied boot.firm from the SDMC folder in the Release .zip to the root of your SD card
Press (Start) to save and reboot
If you get an error, just continue to the next page
At this point, your console will boot to Luma3DS by default.
Luma3DS does not look any different from the normal HOME Menu. If your console has booted into the HOME Menu, it is running custom firmware.
On the next page, you will install useful homebrew applications to complete your setup.
Section IV - Uninstalling MSET9
Do NOT skip this section. If you do, applications may crash.
Power off your console
Insert the SD card into your computer
Execute the mset9.py script on the root of the SD card
Windows: Double-click mset9.bat
If that doesn't work, shift+right-click empty space in the file explorer while in the root of your consoles SD card, select Open in Powershell/Terminal and enter py -3 mset9.py there
Linux: open a Terminal window, cd to the root of your SD card, then type python3 mset9.py and press Enter
You should see a window that says "MSET9 ... SETUP by zoogie"
