It’s due to a cryptographic library implementation in a controller used in the yubikey. It’s a third party controller, and this isn’t exclusive to yubikeys either, a shitload of other stuff uses the same controller and is likely vulnerable to the same attack.
Also, the attack requires around $10k worth of equipment and physical access to the yubikey, so while a valid attack vector, it’s also not something to get into a panic about.
I went into the article thinking I’d need to replace my keys, and after reading decided I’m a very unlikely target for this attack. My threat model doesn’t include nation states, so I’m gonna keep using my yubikeys for the foreseeable future.
I have been thinking about new hardware key(s) that can handle more than 20 passkeys, but that’s not a high priority for me right now.