GitHub link to Nintendo's claim - all the details you need are here
The emulator forks which are being taken down are as follows:
Despite this, the one fork that continues, and will continue without takedown is Ryubing - by Greemdev. This is created by an original member of the Ryujinx team. It's safe, the code is beyond reproach (and violates zero laws or Nintendo code) and actually brings helpful updates.
Still...shitty news. And more indication that the Switch 2's architecture will be damn similar to that of this current Switch. Them taking emulators down means the upcoming games have a solid chance of being emulatable on release. But...that's my own (and others') conjecture, so we'll see when the time comes.
Why are they hosting their code on Github? Switch to Codeberg or maybe self host. And yes I know Github has the most users but they're dealing with something radioactive.
Codeberg can suffer from the same DMCA requests but at least is not managed by Microsoft. To really avoid(or ignore) DMCAs you need to self-host/use a vps for your own version control tool like Forgejo/GitLab or use a decentralized one like Radicle.