Download the repo (zip link or git clone)
Run custominstall.py with boot9.bin, movable.sed, path to the SD root, and CIA files to install (see Usage section).
Download and use custom-install-finalize on the 3DS system to finish the install.

Setup

Linux users must build wwylele/save3ds and place save3ds_fuse in bin/linux. Install rust using rustup, then compile with: cargo build. The compiled binary is located in target/debug/save3ds_fuse, copy it to bin/linux.

movable.sed is required and can be provided with -m or --movable.

boot9 is needed:

-b or --boot9 argument (if set)
BOOT9_PATH environment variable (if set)
%APPDATA%\3ds\boot9.bin (Windows-specific)
~/Library/Application Support/3ds/boot9.bin (macOS-specific)
~/.3ds/boot9.bin
~/3ds/boot9.bin

A SeedDB is needed for newer games (2015+) that use seeds.
SeedDB is checked in order of:

-s or --seeddb argument (if set)
SEEDDB_PATH environment variable (if set)
%APPDATA%\3ds\seeddb.bin (Windows-specific)
~/Library/Application Support/3ds/seeddb.bin (macOS-specific)
~/.3ds/seeddb.bin
~/3ds/seeddb.bin

custom-install-finalize

custom-install-finalize installs a ticket, plus a seed if required. This is required for the title to appear and function.

This can be built as most 3DS homebrew projects with devkitARM.

Usage

Use -h to view arguments.

Examples:

py -3 custominstall.py -b boot9.bin -m movable.sed --sd E:\ file.cia file2.cia
python3 custominstall.py -b boot9.bin -m movable.sed --sd /Volumes/GM9SD file.cia file2.cia
python3 custominstall.py -b boot9.bin -m movable.sed --sd /media/GM9SD file.cia file2.cia

GUI

GUI wrapper to easily manage your apps. (More will go here...)

GUI Setup

Ubuntu/Debian: sudo apt install python3-tk
Manjaro/Arch: sudo pacman -S tk
Mac: Sometimes the default tkinter libs that ship with mac don't work, you can get them on the python site - https://www.python.org/downloads/mac-osx/
Windows: Install python - Remember to install tcl/tk when doing a custom installation

License/Credits

save3ds by wwylele is used to interact with the Title Database (details in bin/README).

Thanks to @LyfeOnEdge from the brewtools Discord for designing the GUI. Special thanks to CrafterPika and archbox for testing.

Thanks to @nek0bit for redesigning custominstall.py to work as a module, and for implementing an earlier GUI.

Thanks to @BpyH64 for researching how to generate the cmacs.