> If you want to use a USB security key, you still can--Passkeys do not take away from that.

I can't. Most of services I use do not support using Passkeys + a USB security key as second factor.

I'm very happy to use Passkeys (synced with my password manager, just like how I sync my password database now) + a USB security key. Unfortunately, most services force me to use Apple (or Google, Microsoft)-implemented Passkeys which are secured by their hardware devices so that they can also function as a second factor.