This is an experimental sysmodule that allows capturing the running game output on a pc.
As this uses switch's built-in game recording feature it has the same limitations: 720p@30fps and only works on the games that enable it, but by sending the video to another device there's no time limit to the recording.
There are two modes: USB and Network, both work fine but USB is slightly better, at least compared to wifi, didn't try with a LAN adapter.
Players like mpv or vlc can play the stream directly so you can use any screen recording applications but it's also possible to write the stream directly to a file, in that case video format is raw h264 data, you can convert it to mp4 with ffmpeg and audio is a stream of uncompressed 16-bit little-endian stereo samples at 48kHz, you can play it with audacity.
To use the USB version you need the UsbStream program you'll find on the github page, it's built using .NET core 3
and works on both windows and linux, haven't tried mac but in theory it should work too.