I'm not an expert, but it's frustrating to read these threads about passkeys. The common objection I see here is "But if I lose my device I'm locked out!"

A lost passkey should be treated the same as a lost password.

Sites that implement passkeys need to have an account recovery mechanism. Granted, not every site does this correctly. Don't use passkeys on sites that don't have a recovery mechanism!

Secondly, the site you're authenticating to must allow you to have multiple passkeys. You either have a cloud-synced password manager so that all of your devices get the same passkey, or you have a passkey per device that you use to access the site. Again, not every site allows multiple passkeys. Don't use passkeys on sites that don't allow you to have multiple passkeys.

For a site implements both of these properties correctly, if you lose your device, you just connect to the site with your new device, perform whatever account recovery procedure (TOTP, email verification, phone verification, ...), create a new passkey, and, ideally, disable the passkey from your lost device.