https://github.com/exelix11/SysDVR says hiThere is currently no homebrew app that can do this.
Switch OS (horizon) has a really strict and complicated security. Running such a homebrew app will cause massive performance and compatibility issues with games (lag and high latency included).
Even if thats doable the switch would have to compress and record video, audio and input (bi-directional) at the same time and send it as a stream through the usb port. Due to the limited bandwidth and ressources the switch has you would have a really crappy picture and most likely input lag in hundreds of msec.