Did you try this https://github.com/thesourcerer8/altium2kicad ?
With NDS TV Out only one screen (with possibility of swapping screen). It's a limitation of the SoC.
We have released a patch for the firmware to have the functionality without having to do the button combination and without having to use the homebrew. I don't know if you've seen it https://github.com/LostNintendoHistory/Lost-NDS-TV/tree/main/fwpatch
You can see here a test:
EDIT:
@Luca
did...
I am doing that. It's a lot of work but now I have some parts of schematics. You can follow my work in this thread of my twitter:
Thanks so much to KreativDax