If SQRL was adopted, then the popular manifestations would have just as much vendor lockin, with built in password managers hosting the master private key without export option.

Passkey is not inherently vendor lock in. It’s mostly a consequence of password managers doing software passkeys and not making it reasonable to export private keys. It does have a mechanism a site can use to lock to “trusted vendors”, but if a site does that, that is on them for being dickish.

Passkeys cross vendor sync is in the works right now and you can already self host with Bitwarden