Passkeys are an implementation of FIDO2 so yes, any sites that have implemented webauthn will support passkeys.

It might be useful to think of passkeys as a usability extension to webauthn. You no longer need to buy dedicated security devices but can use your existing laptop and phone to login securely to your accounts. I expect my parents will start using passkeys on sites in the next 24 months. I would not have tried to get my parents to use Yubikeys.