Passkeys can be a pain in the ass too. Evidentially I set up my Yubikey with Github as some point, which is fine if I'm at my desktop where my key is plugged in, but if I want to sign in on mobile.... now what? I just couldn't log in on mobile for months until I realized I think there's a button on there somewhere that's like "use different 2fa" but then what was even the point of having a key registered if it can be bypassed.
While you can setup passkeys with YubiKey, the most common intended use case is key pairs that are synchable via your Apple/Google/password manager account. So, once you add a passkey, you'll be able to sign in on mobile with it automatically.
you can use yubikeys for both passkey and password+2fa. this way you aren't bypassing anything. and btw, you can get USB-C yubikeys so you can plug it into your phone. if even that's not an option, you can get a USB-C to USB-A adapter.
