At IRC I was told that I might want to ask here and that the icon is representation of two-factor authentication, but in my opinion it shouldn't be used unless Webmin actually supports YubiKey.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi,
I asked at IRC how do I setup YubiKey as two-factor authentication with webmin. The logo for two-factor authentication at webmin is clearly YubiKey (see https://store.yubico.com/store/catalog/images/black_single.jpg ),
At IRC I was told that I might want to ask here and that the icon is representation of two-factor authentication, but in my opinion it shouldn't be used unless Webmin actually supports YubiKey.