Since we are really talking about WebAuthn and not just the iOS implementation, You probably could use alternative hardware (maybe android based) that supports

Since we are really talking about WebAuthn and not just the iOS implementation, You probably could use alternative hardware (maybe android based) that supports the multiple-user biometric use-case. From the server/web-app side it still would just be WebAuthn. Looks like you use a separate device like this: https://www.ftsafe.com/Products/FIDO/Bio https://www.ftsafe.com/Products/FIDO/Bio That supports fido2, hooked to any tablet to make it work.