NintendoSDK

The NintendoSDK is the Software Development Kit for the Nintendo Switch. Its name is generic because it was apparently being developed before the NX (the INDY), and was even used for BoTW on Wii U. It is also called the “nnSdk” due to it using the “nn” namespace, shared by the 3DS SDK.

The NintendoSDK usually refers to itself by the same name, and not specifically the Switch or NX’s SDK.

"GfxPrimitiveRenderer" sample from the SDK.

Switch firmware versions (from switchbrew.org System Version Title)

The firmware for Switch consoles is called “NintendoSDK Firmware for NX”, same for “Ounce”, the Switch 2. This is the same on dev and retail units.

The Switch 2 dev unit has "NintendoSDK Firmware for Ounce".

The SDK features Mii support bundled into the public SDK for all developers: nn::mii

It supports building for NX, and Windows x86/x64. This means that all nn::mii samples run on PC.

MiiShaderSample from the NintendoSDK running on Windows.