We are currently testing adfs 3.0 on our internal portal. Works fine to access it through any browser using my Active Directory log in. (I'm allowing both AD and Portal managed logins until we get any problems worked out)
I can also log in to our portal through ArcGIS Pro using my Portal managed username and password. Our ArcGIS Pro license is still managed by AGOL so there aren't any licensing issues.
However, when I try to login to our portal through PRO using my AD credentials I get the following page after entering in my email and password:
I'm guessing I'm just missing some IIS setting or maybe a setting in adfs, I just don't know what it is.