@sanderev
Nintendo did not DMCA the original Ryujinx project because they had no grounds to do so. Github maintains a repository of DMCA takedown requests it has processed, and uses these to make such affected repositories publicly unavailable. Ryujinx is not among these, however Yuzu is. You can search for “nintendo.md” to see all of the DMCA requests that Nintendo have filed, and the large number of Yuzu mirrors and forks that have been struck down.
At most, they could probably DMCA the /shell.png image featured in the Ryujinx repository’s readme.md, as it depicts partial screenshots and app icons for Super Mario Odyssey, Luigi’s Mansion 3, Splatoon 2, Pokémon Sword, The Legend of Zelda: Breath of the Wild.
They might be able to claim something about their Github Wiki’s guides on dumping Switch firmware and keys, but I’m not sure.
They make their position clear that they do not support piracy and will not tell you where to illegally obtain Switch software, firmware, or keys. The emulator operates on the principle that you provide your own using your own Switch hardware and legally purchased software.
Nintendo are unhappy with the fact that Ryujinx can be abused to circumvent copy protections, and that it has to implement keys to be able to load and play the games, but I don’t know if they can legally do anything about it other than strong-arm people through whatever legal inch they can get.