For the smartphone case, why would I want to pay for Keyri, rather than use WebAuthn (for the web) or the smartphone OS-provided FIDO2 feature that ships with the OS? https://developers.google.com/identity/fido/android/native-a...
Keyri makes less sense for smartphone-only applications. The primary case we solve for is applications that have both mobile and desktop web interfaces. Phones are already essentially considered trusted devices, whether auth there happened via password, SMS OTP, OpenID, FIDO2, etc. Keyri bridges the "trust gap" between the trusted smartphone in the user's hand and the untrusted desktop computer / smart TV / whatever…
Specifically, how does the phone know which web page its owner is looking at on their laptop when they scanned the QR code ? You need to arrange that it's not possible to take the QR code generated for you and present it to a sucker for them to scan instead so that you're signed in as them and like I said, if Keyri does that then I don't see how.