This is my fundamental problem with passkeys: I don't want to use any syncing service.
To be clear, I don't want to deprive other people of the ability to sync their credentials; I simply want to opt out myself. I just want to be able to manually back up and restore my credentials, like I've always done with passwords, but the passkey vendors seem to want to refuse to give anyone this ability. The vendors claim that this is to make phishing impossible, but I abhor paternalism in all forms, and also it's suspicious that this paternalism forces people to use the syncing systems of the passkey vendors, which are usually paid subscriptions. So passkeys become an endless supply of money for the vendors.
It's very telling that passkeys were designed and shipped without any export/import mechanism. You can plainly see the priority of the passkey vendors, which is to lock you in. Allegedly, export/import is coming sometime in the future, but I strongly suspect that they'll end up with some kind of "approved provider" system so that the big passkey vendors can retain absolute control and avoid giving power to the users.
If I were more conspiracy minded, I would suspect some sort of agent provocateur ruining our standards. However, I am unable to come up with a profit motive, so my only conclusion is incompetence.
SSH keys (and any other keypair shared across services) are a non-starter on the web for privacy reasons. (See also: `ssh whoami.filippo.io`.)