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.
Right, Dolphin had an encryption key in there for the Wii that was hardcoded in. That is apparently the one bit of legal leverage Nintendo has to keep it off Steam, though being Nintendo, they would likely fight it, anyway.
In any case, the key could be a user provided configuration option, or tools for ripping games could do the decryption on their own. Either should keep the code safe from Nintendo being able to win a case. Though again, doesn't stop Nintendo from trying and exhausting your ability to fight it.