alt Hacker NewsThere is a project under way to specify how to "sync" device-bound keys between authenticators: https://fidoalliance.org/specs/cx/cxp-v1.0-wd-20241003.html
Ideally this should have been hashed out before deploying passkeys everywhere, but I guess you can always register multiple passkeys for the sites that allow you to.
Iirc the original idea was that passkeys should be device specific. Of course that's impractical so now they're morphing to a long password that a human can't process.
In a few years someone will post "how about a long human retainable passphrase?" as a new and improved discovery.