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Google will now make passkeys the default for personal accounts
(arstechnica.com)
This is a most excellent place for technology news and articles.
Apple is quite dogmatic in that their implementation demands cross device syncing.
It's definitely possible to have such an implementation and those will be the most common. You take a very small security risk for a huge convenience factor.
For the more paranoid, device-bound passkeys do not sync. If you lose the device, you will need to go through a recovery procedure.