The word "INTERNAL" signifies proprietary materials never intended for public release. "3DS INTERNAL" typically denotes:

Preserved in its original "Internal" release format for archival accuracy.

Develop tools like Luma3DS by seeing how official system updates were signed.

A nuanced argument exists for the "fair use" of such tools:

is it possible to use the retail N3DS as a devkit? : r/3dshacks

: A standard application on development units (Panda or Snake units) used to install and manage software, including Config Menu

Instead of "guessing" how to use the hardware, homebrew developers could look at official implementation patterns to create smoother, more stable apps. Legality and Ethics

Utilities used to generate manual files, icons, and banners for the 3DS HOME Menu.