In terms of SSH, one of the features of Duo is that you can have many methods to authentication... push to phone, phone call, sms, yubikey, etc -- having that list allows you to pick how upon login.
We're definitely a SaaS provider so going through us is part of our service -- this also allows us to handle things such as telephony needs, push notifications, etc. for customers.
In terms of technical information, is there a specific feature or technology you're interested in knowing more about?
According to the SSH screenshot you gotta choose the auth type, then enter the password or wait for auth.
In every case their central server seems to have authority over the 2nd factor, too.
Also, even the whitepaper is advertisement bullshit, no technical info. Is there any technical info anywhere?