As of Mid 2026, it doesn't work at all on Kubuntu 26.04 and Firefox 152. However, with the help of Claude and a few system tweaks the webAuthnLinux popup does happen and accepts my finger print from fprintd-verify. It then sends 'a result' back to webauthn.io.
However more recent versions of firefox are more strict on security and therefore the packet sent back is rejected by webauthn.io due to firefox strict security.
It therefore needs updating.