Here is a simple console application to record a Spout source to video using FFmpeg.
It’s an example of receiving from a Spout source without dependency on OpenGL, DirectX or Windows and using FFMpeg for real-time encoding. For those familiar with FFmpeg, various options can be explored with command line arguments by using a batch file, such as encoding with x264, x265 and Prores.
Those not so interested in these things, can still try it out by downloading the release and following the instructions or look at the LightJams Spout recorder or OBS studio with the Off World Live Spout plugin. Other applications also provide directly for Spout input and video recording.