Atmosphère
Atmosphère is a work-in-progress customized firmware for the Nintendo
...The project is composed of multiple subsystems such as Fusée for bootloading, Exosphère for secure monitor customization, and Stratosphère for system module extensions. It provides a foundation for running custom applications, modifying system behavior, and experimenting with low-level features of the Switch hardware. Atmosphère is actively developed and updated to maintain compatibility with new firmware versions while improving stability and performance. It is widely used in the homebrew community as a base platform for building tools, mods, and custom applications.