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.
Ideally, some of this could actually be solved by having a government organization that provides this and is regularly updated / audited etc. but in the US at least, we are not in any place for that to happen, so you need to pick a provider.
Apple is reasonably good at this, if you're in their ecosystem. Can't speak for Google. 1Password has been very good to me as well, and there are Yubikeys too.
Nothing is perfect, but this is a far, far far better state than were it was heading before WebAuthN