Have you heard of the JumboTron DS? It's an amazing modification made by a Japanese guy posted on Youtube a long time ago, in the video description there's a link that doesn't work anymore (but thanks to the Internet Archive we can see the content) that shows the step by step of how to make a GIANT DS AND FUNCTIONAL, being able to even take screenshots of the game (I don't remember if it is possible to record the screen, I think so), and years later they discover that it is possible to play DS on the TV by soldering something on the board, it would be this old project of a Japanese to solution to record gameplay directly from the console? I would love for someone to translate the walkthrough on his website so I can try it on my console too!
You can take a look at the JumboTron in this video here:
You can take a look at the JumboTron in this video here: