Earlier quoted context omitted.
You shouldn't ~~necessarily~~ need to "sync" your passkeys across all your devices; each device should have its own passkey. Then if you lose a device (or that one device gets compromised), you revoke the one key and everything else is fine. Similar to SSH keys. No reason to use the same key on all your machines, use a different key from different places. The passkeys on my laptop are different from the passkeys on m…
Great in theory, but in practice there are still a frustrating amount of websites and services that put a low upper limit (usually just one or two) of the number of keys you can enroll. This effectively makes it impossible to do what you’re saying. It sucks.
Every other site I've come across that supports these things supports multiple. What common sites support only one or two?