[awegio]

It depends on your web browser. Just see what happens here https://webauthn.io/

Firefox on Desktop tells me to "touch my security key". Not sure how that works. Firefox Android gives me a few hardware options to store my passkey to. Chrome Desktop asks me to enable Bluetooth. Chrome Android asks which Google Account to use.

[Izkata]

Just tried that with Firefox on Android and while it works, I can't find any evidence of a stored passkey on my device, let alone a way to export it.

[grotorea]

Are on Linux? AFAIK it doesn't work on Desktop Linux.