I don’t believe there’s support within the plugin itself to use anything other than Lock in the login page that gets shown within Wordpress itself, however, if in the plugin advanced settings you enable the Auto Login (no widget) toggle and then proceed to fill the Auto Login Method with the name of your ADFS connection this should mean that the Lock widget would not be shown directly in Wordpress and instead you would be redirected to the authorization endpoint when you trigger a login in Wordpress.
I tested the above using a database connection and it worked as expected from the sense that it did not show Lock in Wordpress. Granted that this means that the user will likely be shown the custom hosted login page which by default also uses Lock, however, the hosted login page can be fully customized so I believe that ability would allow you to meet your particular requirements. As a disclaimer, I never tried this myself, but in theory it may be helpful for your scenario.