Great resource! But a lot of it is very old. I recently discovered this open source ds cart[1] and an alternative SDK[2] to devkitPro. Both were used in the development of a demo[3] released at Revision this year.

[1]: https://www.lnh-team.org/

[2]: https://blocksds.skylyrac.net/

[3]: https://www.pouet.net/prod.php?which=105928

I had a go at setting up the devkitpro stuff and building a demo that I run on my DS. It’s surprisingly easy to do and kinda neat.