NTR CFW (BootNTR Selector) is a custom firmware designed for the New 3DS, with the following features:
Backlight Control, Streaming, Real-time Saves and Multi-Language Support are just some of the features and reasons people use NTR CFW.
To use Launch NTR CFW from the Homescreen and select the desired version you wish to use (3.2, 3.3, 3.5). If a selection isn’t made quickly enough the default will be loaded.
Now you can press X+Y to load the NTR Menu and take screenshots etc.
Developer Page: https://github.com/Nanquitas/BootNTR/releases
Boot NTR Page: https://github.com/44670/BootNTR/releases
Read the manual for details on How to Stream: